CHAPTER XI._Glue, gelatine, animal charcoal, phosphorous, cements, pastes and mucilages

TESTING GLUE AND GELATINE.

It is of importance that the manufacturer as well as the dealer should

know how to test the quality of a glue. This may be done by chemical

means and in a mechanical way.

_Determination of moisture._ For this purpose a weighed quantity

of the sample, finely powdered, is for fourteen hours exposed to a

temperature of 217° to 230° F. It is then cooled under the dessicator

and reweighed. The content of moisture is then calculated from the loss

in weight.

_Determination of ash._ The origin of a sample of glue may be traced

by examining the ash for phosphates of lime and magnesia, bone-glue

containing both, while skin-glue is free from phosphates. Reduce

a portion of the sample to a fine powder, and weigh it in a tared

constant crucible. Heat slowly over a Bunsen flame until carbonized,

then remove the crucible to the muffle, and heat to bright redness for

10 hours. Cool under the dessicator and weigh. The increase in weight

of the crucible is the ash of the sample. This will vary from 1 to 2

per cent. in a gelatine, 2 to 3 per cent. in a good glue, 6 to 8 per

cent. in a common quality.

_Determination of Acidity._ Kissling elsewhere determines the acidity

by suspending 30 grammes of the sample in 80 Cc. of cold water for 10

to 12 hours in a flask connected with a condenser. The volatile acids

are then driven over by a current of steam into a graduated cylinder.

When the distillate amounts to 200 Cc., distillation is interrupted,

and the distillate treated with standard decinormal alkali. When the

distillate contains sulphurous acid, a known quantity of the standard

alkali is previously added to the cylinder.

An undue quantity of acid may be detected by the taste. Glues may be

alkaline from the addition of excess of lime in the manufacture to

correct the sourness of the jelly. For uses where colors are concerned

the glue must be neutral to litmus; for adhesive uses this does not

matter unless the alkalinity or acidity is due to defective preparation

(Samuel Rideal).

_Determination of Glutin._ The percentage of glutin in a glue solution

is determined by precipitating it with tannin. The dense white

precipitate formed is thrown on to a tared filter, washed with hot

water, dried and weighed. The calculation is made on the basis that the

tannate of glutin has a percentage composition of 42.74 per cent. of

glutin and 57.26 per cent. of tannin.

Bisler-Beumat while employing the same principle prepares two

solutions: _a._ 10 grammes of pure tannin to the liter. _b._ 10 grammes

of pure isinglass and 20 grammes of alum to the liter. The ratio in

which the tannin is precipitated by the isinglass solution, which

Risler considers as pure glutin, is then determined by titration. The

tannin solution is then diluted so that exactly an equal volume of glue

solution is precipitated by it.

In order to test a sample of glue, dissolve 10 grammes of it together

with 20 grammes of alum in a liter of water, heat being applied if

necessary. Next 10 cubic centimeters of the tannin solution are taken

to which an equal bulk of glue solution is at once added, as one may be

sure that this quantity is not sufficient for the precipitation of the

measured quantity of tannin, because no glue found in commerce is as

pure as isinglass. The vessel containing the mixed liquids being well

shaken and the precipitate having subsided, another cubic centimeter of

glue solution is added to the tannin solution which is next filtered

through a moist cotton filter. If _one_ drop of the glue solution still

produces a precipitate in the clear filtrate, another cubic centimeter

is added to the tannin solution, and then again filtered, these

operations being repeated until the filtrate is no longer rendered

turbid by the glue solution.

With the known relation of the tannin solution to pure glue

(isinglass), a conclusion may be formed from the number of cubic

centimeters of glue solution used as to the content of glutin in the

sample examined.

The percentage of glutin varies, of course, according to the quality

and origin of the glue. Bone glue of good quality contains from 50 to

52 per cent. and skin glue from 65 to 75 per cent.

S. Dana Hayes analyzed two samples of American glue of best quality and

obtained the following results:

a. b.

Water (escaping at 212° F.) 16.70 16.28

Glue substance 79.85 80.42

Calcium carbonate 1.42 1.33

Calcium sulphate 0.41 0.34

Magnesium phosphate 0.35 0.31

Alkaline salts 0.17 0.12

Silica, ferric oxide, etc. 0.09 0.08

Zinc oxide 1.01 1.12

The chemical modes of testing glue give only the quantity of glutin

contained in it, but do not prove that the substance combined with

tannin corresponds to the actual adhesive power of the glue, for it is

possible that a glue containing a large quantity of glutin may possess

but little adhesive power, and a jelly from which the glue is formed

may contain an equal amount of glutin with the latter, but not possess

an equal power of adhesion.

It is certain that the determination of the glutin alone is not a

criterion of the quality of glue. In the absence of a reliable method

of direct analysis, attempts have been made to deduce the quality of

glue from indirect properties.

One of these methods consists in immersing the sample of glue in a

large quantity of water at 59° F. for a considerable time. The glue

swells up, absorbing 5 to 16 times its own weight of water. The

more consistent and elastic the glue in this state is found to be,

the greater its adhesive power, and the larger the quantity of water

absorbed the more economical the glue will be in use. This method does

not give thoroughly reliable results, and should only be employed with

bone-glue, as skin-glue does not behave in a similar manner.

[Illustration: FIG. 65.]

A more reliable method is to test the strength of a glue by the method

first proposed by Lipowitz, which is based on the weight-sustaining

power of a jelly of known strength and temperature. The test is

executed as follows: Soak 5 parts of the sample in water, then dissolve

it in sufficient hot water to make the weight of the solution equal

to 50 parts, and allow to stand for 12 hours at 64.4° F. in a glass

cylinder of uniform width to gelatinize. Cover the glass cylinder with

a tin cap perforated in the centre, Fig. 65. Through the perforation

is passed freely a stout iron wire, at the lower end of which is

soldered a piece of tin shaped like a saucer, the convex side of it

resting on the surface of the jelly. To the upper end of the wire,

which together with the tin saucer should weigh 5 grammes, is soldered

a funnel weighing 5 grammes, and capable of holding up to 50 grammes

of fine shot. The apparatus is gradually loaded with shot until the

saucer-shaped piece of tin is forced into the jelly. The greater the

strength of the jelly, the heavier will be the weight required. From

the determined weight of the shot used, the relative value of the glue

as to its adhesive power is determined.

The following results have been obtained by comparative experiments

with this apparatus:

Variety of Glue. Weight required to force

the saucer down.

Breslau 1704 grammes = 3.74 lbs.

Russian 1446 grammes = 3.18 lbs.

Cologne 1215 grammes = 2.67 lbs.

Muhlhausen I. 727 grammes = 1.599 lbs.

Nördlingen 724 grammes = 1.592 lbs.

Muhlhausen II. 387.5 grammes = 0.85 lbs.

The results of these experiments agree to a remarkable degree with the

market prices of the varieties of glue, which is not the case with

glues tested by the methods previously mentioned. The results of these

tests are given in the table below:

Table Key:

Variety of Glue.

1. Best White isinglass in three qualities

2. Translucent yellowish bone glue in tablets and easily soluble

3. Pale yellow glue similar to No. 2

4. Brown-reddish, brittle in fracture and soluble

5. Clear translucent glue of medium brown color

6. Brown-yelow glue in thick tablets and possessing but little

translucency

7. Pale brown-yellow glue, readily soluble and elastic before breaking

8. Pale amber-colored glue with but little translucency

9. Brown glue, solution turbid

10. Amber-colored glue, opalizing and readily soluble

11. Thich tablets or dark-brown glue, solution very turbid

12. Dark horn-like glue with little translucency

13. Very translucent glue of a light brown color and very clean

solution

14. Translucent dark-brown glue, giving a very clear solution

----+----------------+--------------+------+-------------+-------------

----+----------------+--------------+------+-------------+-------------

1. | 20 to 21 | 74.62 | 55.69| — |

| | | | |

2. | 13.2 | 76.2 | 56.8 | 40 |64 grammes

| | | | | (2.25 ozs.)

3. | 13.0 | 70.0 | 52.2 | 35 |60 grammes

| | | | | (2.11 ozs.)

4. | 10.0 | 71.0 | 52.9 | 12 |Does not

5. | 11.0 | 71.5 | 53.3 | 20 |20 grammes

| | | | | (0.705 oz.)

6. | 12.5 | 68.0 | 50.7 | 27 |15 grammes

| | | | | (0.52 oz.)

7. | 13.0 | 66.6 | 49.7 | 30 |36 grammes

| | | | | (1.26 oz.)

8. | 9.5 | 68.5 | 51.1 | 33 |60 grammes

| | | | | (2.11 oz.)

9. | 10.0 | 82.0 | 53.7 | 30 |50 grammes

| | | | | (1.76 oz.)

10.| 9.5 | 73.0 | 54.4 | 35 |56 grammes

| | | | | (1.97 oz.)

11.| 13.5 | 64.0 | 47.7 | 18 |23 grammes

| | | | | (0.81 oz.)

12.| 9.0 | 72.6 | 54.2 | 29 |12 grammes

| | | | | (0.42 oz.)

13.| 13.5 | 70.0 | 52.2 | 30 |40 grammes

| | | | | (1.41 oz.)

14.| 15.0 | 66.0 | 49.4 | 25 |42 grammes

| | | | | (1.48 oz.)

----+----------------+--------------+------+-------------+-------------

This table shows the following facts:

1. The percentage of water in the 14 dry varieties of glue examined

varies between 9.0 and 21. The loss of water from isinglass is

surprisingly large, especially as it cannot be explained by an

artificial admixture of water, since the six varieties examined

reabsorbed the same percentage of water from the air. The percentage of

water in the other varieties of glue differs but little.

2. The various varieties of glue required different quantities of

tannic acid for their precipitation, the amount for 100 parts of glue

varying between 66 parts and 76.2, or calculated to per cent., between

49.4 and 56.8.

3. Placed in cold water, glue swells up and absorbs from 12 to 40 parts

of water. The behavior of the various varieties differs very much in

this respect, and in most of the experiments, with the exception of

variety No. 4, the percentage of glutin is in exact proportion to the

quantity of water absorbed.

4. The strength of the gelatinized glue varies between 12 grammes

(185.18 grains) and 64 grammes (987.67 grains) for a 10 per cent.

solution. This property corresponds neither with the absorption of

water nor the percentage of glutin.

Variety No. 4, in the table, contains 52 per cent. of glutin, but does

not gelatinize, its strength being therefore equal to 0, while variety

No. 14, with 49.4 per cent. of glutin, therefore less than No. 4,

shows a strength of 42. As no close connection between the properties

mentioned in the table can be recognized, it is best not to be guided

by these properties alone, but to test also the behavior of the glue in

practical use. Such test consists in estimating the adhesive power of

the glue from the weight required to tear asunder two pieces of wood

glued together and dried. But as the results obtained by this purely

practical test must necessarily vary on account of the impossibility of

having two surfaces of wood always exactly alike, and the uncertainty

of applying every time the same quantity of glue, Weidenbusch’s method

may here be given. It is based upon the principle that sticks of

plaster of Paris cast of exactly the same material and of uniform size

break under the same weight when placed upon two supports and loaded in

the centre. If now such plaster sticks be saturated with glue solutions

prepared according to the same method, but from different qualities

of glue, a greater force will be required for breaking them, and this

force will be the greater the better the quality of glue is.

The plaster sticks are prepared as follows: Reduce pure crystallized

gypsum to a fine powder, pass the latter through a sieve having 324

meshes per square centimeter and heat it to between 284° and 302° F.

For casting the sticks moulds of soap-stone are used. The moulds are

made by boring in a piece of soap-stone, at a distance of about 1

centimeter from each other, holes with a diameter of 6 millimeters on

top and 7½ millimeters on the bottom.

The gypsum is weighed off in portions of 1 gramme each, mixed with 1

gramme water and cast in the moulds. The solidified sticks are first

dried at a moderate heat and then over calcium chloride, and kept for

use in an air-tight vessel.

[Illustration: FIG. 66.]

The glue solution is prepared as follows: The glue dried at 212° F. is

weighed, soaked over night in water, then melted in a small glass in

the water-bath, and finally enough water is added so that the solution

contains 10 per cent. of dry glue.

The plaster sticks are for one or two minutes immersed in the glue

solution heated to 212° F., and then placed vertically upon a glass

plate until superficially dry, when they are completely dried at 212°

F. It is recommended to color the glue solution with indigo, the

uniform saturation of the sticks being thereby more easily recognized.

The apparatus for testing the strength of the sticks consists of a

brass ring _a_, Fig. 66, having two notches to receive the stick, and

its diameter is divided into two equal parts by an indicator. The ring

is supported by a pin, by means of which it is secured in a stand. The

apparatus is completed by an iron or glass cup which is suspended by

three cords, _i_, and the hook _f_ to the plaster stick _b_. The hook

_f_ is placed in the position indicated by the indicator. Mercury is

now poured into the cup until the plaster stick commences to break. The

weight required is recorded and compared with a standard glue. During

the experiment the cup is suspended by the three cords _h_ to the ring

_a_, and is thus caught when the plaster stick breaks. On the lower end

of the cup is a clip for emptying the mercury into a vessel so that

none of it is lost.

The “Artillery Werkstätte” at Spandau has adopted the severing strain

of two blocks of wood glued together. The test is executed as follows:

Three parts of glue (but not less than 250 grammes) are mixed with

6 parts of water and boiled in a steam bath until the weight of the

boiled glue amounts to only 5/9 of the original mixture. The reason for

this continued boiling is to ascertain whether the glue to be tested

retains the required adhesive power even after six hours continued

heating in a steam bath as frequently happens in the workshop. With the

glue thus prepared the following breaking test is made:

Blocks of hard or soft wood 420 millimeters long and 40 × 40

millimeters cross section are cut in two, so that each piece thus

obtained is 210 millimeters in length. These two pieces are then again

glued together across the grain with the glue to be tested. The

block is then placed in a dry room at a temperature of 62° to 68° F.

for 72 hours, when the joint is tested as to its resisting power. At

a distance of 180 millimeters from the joint a hole is bored in the

block. Through this hole is pushed a bolt furnished on the lower end

with a hook to which a scale is suspended. The block of wood is clamped

to a table so that the joint projects 1 centimeter beyond the edge. The

scale is at the start loaded with 25 kilograms, the load being every

five minutes increased 5 kilograms till fracture takes place.

Two such blocks, one of hard and one of soft wood, are subjected to the

test, and a serviceable glue must stand at least an average load of 70

kilograms.

_Determination of adulterations._ White lead, sulphate of lead, zinc

white, or chalk in quantities varying from 4 to 8 per cent. are

frequently mixed with the melted glue to improve the appearance of the

finished product. Thus, according to analyses by A. Faisst, Russian

glues contained in 100 parts foreign admixtures as follows:

I. II. III. IV.

Zinc white 1.66

Chalk 2.40 2.95 3.79 2.10

Sulphate of lead — 4.16 2.35 3.18

—— —— —— ——

4.06 7.08 6.14 5.28

The so-called patent glue which is opaque and of a white color is

produced by adding considerable quantities of white lead to ordinary

glue.

According to Barreswil, glue is frequently mixed with lead acetate

solution to protect it from putrefaction. Such an addition, as well

as the presence of white lead or sulphate of lead, is detected by the

introduction of sulphuretted hydrogen into very dilute glue solution.

In the presence of lead acetate a black precipitate of lead sulphide

appears in the clear solution; if white lead or lead sulphate is

present, the white powder settling on the bottom is blackened by the

formation of lead sulphide.

For the detection of other earthy additions, prepare a very dilute

solution of the glue in question and allow it to stand quietly for

a few hours. The heavy additions subside, and after decanting the

supernatant fluid is collected upon a small filter and examined by the

customary analytical methods.

It is difficult to say what quantities of earthy constituents actually

constitute an adulteration, since it is claimed by many practical men

that a considerable content of earthy parts is of advantage as regards

the cementing power of glue. Generally speaking it may, however, be

said that a glue containing more than 6 to 8 per cent. of earthy

constituents must be considered adulterated.

For many purposes, especially if the glue comes in contact with colored

materials as, for instance, in book-binding, a content of free acid

would exert an injurious effect upon the colors, destroying or changing

them. It is therefore advisable to test the glue with blue litmus paper

which, in the presence of free acid, is reddened.

In testing a large number of samples of glue, Kissling obtained the

following results:

Number Smallest Largest Average

SKIN GLUE. of samples. percentage. percentage. percentage.

Water 15 13.4 18.1 15.7

Ash 16 1.0 4.13 2.15

Fat 21 0.01 0.090 0.037

Volatile acids, free } 8 {0.084 0.238 0.178

Volatile acids, fixed } {0.084 0.334 0.191

BONE GLUE.

Water 25 11.5 17.7 13.4

Ash 26 1.16 5.07 2.46

Fat 5 0.047 0.217 0.113

Volatile acids, free } 7 {0.088 1.451 0.655

Volatile acids, fixed } {0.097 0.721 0.460

However, those who from their practical knowledge are most competent to

judge the commercial value of a glue, scarcely require such complicated

tests, as by taking the sample in their hand and looking at it,

they can in most cases tell its quality. Great hardness, a clear,

rattling sound when struck, and resistance to breaking are signs of

good quality, and if the cake is cut thick, it shows that the jelly

possessed great consistency. Many kinds of glues are intentionally

cut thin so that they will dry before spoiling. The derivation of

a glue from a sound jelly is recognized by the fine cutting lines.

When the jelly possesses but little gelatinizing power and is in the

first stages of decomposition or putrefaction, or formation of sugar

has already set in, it cannot be poured into moulding boxes, as it

would putrefy before it has a chance to gelatinize. Such sick jelly is

poured in thin layers upon glass or metal plates so that it may acquire

sufficient solidity to allow of its being cut up into leaves and dried

upon nets. If the edges of the glue are deeply indented and raised, the

jelly, before drying, possessed but little concentration (25 to 30 per

cent.), and if notwithstanding this, it acquired sufficient consistency

to allow of its being cut, it must have been very sound. Glues cut

thick and showing no indentations and raised edges, are derived from

excessively concentrated jellies (30-35-40 per cent.). Such jellies

lose in quality in evaporating.

A high degree of transparency is a favorable sign as regards the purity

of a glue, substances inducing putrefaction having been eliminated.

Hence this property should be worthy of recommendation, but the

consumer having been disappointed in the use of thin glass-clear glues,

distrusts also the thick-cut transparent product, preferring a turbid,

translucent or opaque article. For this reason the manufacturer is

forced to render glass-clear glue turbid with coloring matter.

The color of the glue is also a means of judging it. To be sure,

chemically pure glutin is a colorless substance, but glue is always

colored more or less dark brown. Although this coloration does not in

the least impair the adhesive power, the manufacturer endeavors to

produce a product of as light a color as possible, and this is best

effected by bleaching with sulphurous acid. By this means the glue not

only acquires a lighter color, but also becomes more stable, substances

inducing putrefaction being destroyed by the acid.

PART II.

CEMENTS, PASTES, MUCILAGES.

CHAPTER XII.

CLASSIFICATION OF CEMENTS.

The great variety of substances entering into the manufacture of

cements and pastes makes a division of them extremely difficult.

Stohmann divides them into the following groups:

1. _Oil cements._

2. _Resinous cements._

3. _Cements containing rubber or gutta percha._

4. _Cements containing glue, or starch paste._

5. _Lime cements._

Generally speaking, this division is correct; the only change we

would suggest is to apply the term _agglutinant_ or _paste_ to bodies

containing glue and starch paste.

When we attempt a division of the cements according to the bodies to be

cemented, we find that the result will be a larger number of groups;

as we must take into consideration whether the articles to be cemented

have to be heated or not, whether they are to come in contact with

water or other liquids, and other circumstances which would necessitate

modifications in the composition of the cements themselves.

According to this, we might group the cements as follows:

1. _Cements for glass and porcelain, for repairing broken articles,

for fastening glass letters upon show-windows, etc._

2. _Cements for metals not exposed to an increase of temperature, for

instance, for tightening the joints of gas and water pipes._

3. _Cements for stoves and other articles, which have to stand an

increased temperature._

4. _Cements for chemical apparatus, i. e., such as will have to resist

the action of chemical agents._

5. _Cements to protect vessels of glass, porcelain, or metal against

the action of fire._

6. _Cements for filling hollow teeth, for microscopical preparations,

and other delicate articles._

7. _Cements for special purposes, for instance, for cementing

meerschaum, tortoise shell, etc._

_Chemical nature of cements._ The different varieties of cement

frequently contain substances which act chemically upon each other,

or upon the bodies to be united with them. To determine the practical

availability of a variety of cement for a determined purpose, it is of

importance to know the reciprocal behavior of these substances towards

each other, as from this we are able to judge at once whether a cement

is suitable for a certain purpose or not.

_Oil cements._ The fluid fats, commonly called oils—though there are

oils which remain solid at the ordinary temperature, as, for instance,

palm oil and cocoanut oil—may, as regards their behavior on exposure to

the air, be divided into two large groups, namely, drying and nondrying

oils. As samples of these groups may be mentioned olive oil and linseed

oil.

If a thin layer of olive oil protected from dust is exposed to the

air, it will remain fluid for years and retain its characteristic oily

consistency. The only change it undergoes is that it becomes somewhat

more viscid and rancid, and acquires a darker color, but it never dries

up.

Linseed oil treated in the same manner solidifies in the course of a

few weeks to a hard, tough and elastic mass, resembling, as regards its

physical qualities, resin or rubber.

By compounding a drying oil with a small quantity of litharge,

pyrolusite, manganous borate, etc., and heating the admixture to the

boiling-point, it acquires the property of drying in a few hours when

exposed to the air in a thin layer. Oil so treated has been changed to

a varnish.

By bringing a drying oil in contact with a body possessing strong basic

properties a peculiar process takes place; the sebacic acids contained

in the oil combine with the basic bodies to solid combinations which

are insoluble in water, and, on exposure to the air, change gradually

into masses as hard as stone. Such combinations, as regards their

chemical composition, resemble ordinary soap, and for this reason are

called insoluble soaps to distinguish them from ordinary soap which is

soluble in water.

Burned lime, calcined magnesia, whiting, ferric oxide, litharge, and

minium possess the capacity for forming insoluble soaps on coming

in contact with drying oils and, still more quickly, with varnishes

prepared from them.

The hardness of these soaps in time increases considerably by the oil

not saponified drying in. The oil cements are principally used for

tightening water and gas pipes, as they resist the action of water,

steam and gas.

The only drawback connected with these cements is that they must reach

a certain age before becoming entirely hard, and that, on account of

the high price of drying oil or varnish which is absolutely required

for their preparation, they are rather expensive. The ordinary

glazier’s putty and the red lead and linseed-oil cement used in

constructing water and gas conduits belong to this group.

_Resinous cements._ By resins are understood a number of constituents

of plants which exude in thick viscous masses through incisions made

in the trees, and on exposure to air are gradually converted into

less transparent, brittle masses. When heated they melt more or less

readily, forming a thick, ropy liquid, and brought in contact with an

ignited body they burn with a bright flame and much sooty smoke.

By making incisions in the bark of any of the whole genus of _Pinus_

belonging to the _Coniferæ_ family, a viscous mass of a strong odor,

called turpentine, is obtained. It consists of a solution of common

rosin in the essential oil of turpentine, and when distilled yields

from 75 to 90 per cent. of colophony or rosin, which remains in the

retort, and from 25 to 10 per cent. of the essential oil, commonly

called spirits of turpentine. Pure rosin is a brittle, tasteless, and

almost inodorous mass of a light yellow color and a smooth, shining

fracture.

The various resins found in commerce, such as shellac, mastic, elemi,

copal, etc., are formed in a similar manner.

The principal points of importance for our purpose are the different

degrees of hardness and brittleness and the melting-points of the

various resins. While some possess but slight hardness, for instance

elemi, others, such as copal and amber, excel in this respect and their

brittleness and high melting-point.

To decrease the brittleness of resins, essential oils are sometimes

added, or resinous cements are mixed with oil cements or a fat drying

oil, or compounded with rubber cement.

Resinous cements are either softened by heating or entirely melted,

or solutions of resins in volatile solvents are used, which, in

evaporating, leave the resin behind.

The resinous cements possess great power of resistance, and are

therefore well adapted for tightening water and gas pipes, but they

have the disadvantage of not standing a high temperature and possessing

a certain degree of brittleness which renders them unfit for the

cementing of articles exposed to frequent shocks.

Many of these cements, especially those prepared with pitch or

asphaltum, can be produced at a very low cost, and do excellent service

for water-proofing vessels, water-reservoirs, brickwork, etc.

_Rubber and gutta-percha cements._ Caoutchouc, commonly called India

rubber, or briefly rubber, is derived from the milky juices of

certain tropical plants. It is distinguished by great elasticity and

indifference to chemical agents.

Both these properties make it a valuable material for cement, and it

is much used for this purpose either in the form of solution or as

a constituent of other compositions. For cements which are to have

a certain degree of elasticity combined with indifference toward

chemical agents, it is absolutely indispensable, as no other known body

possesses these properties in such a high degree.

The derivation of gutta percha is similar to that of rubber. At an

ordinary temperature it forms solid and very tenacious masses, of a

leather-like consistency, but at a somewhat higher temperature (below

the boiling-point of water) it is converted into a very plastic, soft

mass, which can be drawn into very fine threads, and rolled to very

thin plates.

By itself or mixed with other substances it furnishes an excellent

cement, possessing the valuable properties of tenacity and pliancy

when exposed to shocks. As regards resistance to the action of water

and chemical agents it is almost equal to rubber, and, for certain

purposes, is frequently preferred to the latter.

_Glue and starch cements._ By itself, _i. e._, converted by boiling

with water into a viscous mass which solidifies on cooling, glue cannot

be classed with the cements; the same applies to paste, _i. e._, starch

or flour swelled and boiled in water.

But compounded with other substances both yield excellent cements,

in which a part of the properties distinguishing glue solution and

paste is preserved. They both possess the property of decreasing the

brittleness of many cements, but unfortunately the latter thereby lose

their power of resisting the action of water; for starch as well as

glue swells in water, and the latter, when moist, passes quickly into

putrefaction and destroys the cement.

In a wider sense isinglass, compounds of glue and vinegar, of lime and

glue, etc., must be classed with the glue cements, and ordinary flour

and shoemakers’ paste with starch cements.

_Lime Cements._ Lime possesses the property of forming insoluble

combinations with egg albumen or caseine, this being the reason why

lime cements, of which there are a great number, are generally composed

of burned lime and one or the other of the above substances. Lime

compounded with a solution of water-glass forms also very solid and

durable cements.

Although the cements and agglutinants mentioned in the foregoing

are most frequently used, a compound of different cements is often

employed, in consequence of which the composition of many cements is

very complicated.

In the following we give a description of the preparation of the

different kinds of cement, according to the manner of their employment.

CHAPTER XIII.

PREPARATION OF CEMENTS, PASTES, AND MUCILAGES.

OIL CEMENTS.

Oil cements, as already explained, must be considered as a variety

of soaps insoluble in water, formed by the action of drying oils or

varnish upon various basic combinations.

The most important of this class is the cement used for securing

window-panes. Good glaziers’ putty is a product of extraordinary

durability, and, besides for puttying glass and wood, can also be used

for joining many other bodies.

_Putty._ This is prepared by mixing fine whiting with linseed oil or

linseed-oil varnish. The whiting should be passed through a sieve of 42

meshes to the inch. It should be perfectly dry before sifting, and be

thoroughly incorporated with the oil.

As the work of kneading large masses with the hands or feet must be

continued for a long time in order to obtain an entirely uniform

product, and is consequently very laborious, it is recommended to use

the following contrivance:

Two wooden rollers rest in a suitable frame, and can be brought

together or removed from each other by means of two screws. When the

mixture of whiting and linseed oil is of sufficient consistency to

allow kneading, it is fashioned into a cylinder and rolled out between

the above rollers to a long, thin band, which is caught in a vessel.

The band is balled together, the ball reformed into a cylinder, and the

latter again passed through the rollers, the operation of balling and

rolling being continued until a uniform mass is obtained.

The finished product should be kept in oiled paper or under water.

White lead is sometimes mixed with the putty, and other pigments to

give color as desired. Hard putty may be softened by rolling between

the hands.

_French putty._ Boil 7 lbs. of linseed oil with 4 lbs. of burnt umber

for 2 hours. Then add 10 lbs. of white lead and 5½ lbs. of chalk.

_Soft putty._ Whiting 20 lbs., white lead 2 lbs., linseed oil and olive

oil 1 gill each.

Mix the whiting and the white lead with the necessary quantity of

linseed oil, to render the putty of the proper consistence, the olive

oil being added to the linseed oil before kneading. The object of using

olive oil is to prevent the white lead from hardening, and it preserves

the putty in a state sufficiently soft to adhere at all times, and not,

by getting hard and cracking off, suffering the wet to enter, as is

often the case with ordinary hard putty.

_Litharge cement._ By mixing litharge reduced to a fine powder with

linseed oil, a yellow cement is obtained which gradually solidifies to

a mass as hard as stone.

_Red lead cement_ is made by mixing red lead with linseed oil to a

paste. It is used for cementing the joints of metal pipes.

Lead preparations furnish excellent cements, but have the disadvantage

of great weight and a high price. For many purposes a part of the lead

combination can be suitably replaced by a substance of less weight,

such as whiting, or, still better, burned lime slacked with sufficient

water to convert it into a powder.

The quantity of the substitute added varies very much, there being,

for instance, many varieties of so-called red lead oil cement, which

contain only about 10 per cent. of red lead.

_Cement for wash basins._ Finely powdered glass (sifted) 2 parts,

litharge 2 parts, linseed-oil varnish 1 part.

Wet the powders slightly with the oil, heat and gradually add the

rest. Do not use the basin for several days. Finely powdered glass or

glass meal may be made by heating glass, throwing it in cold water,

grinding the fractured pieces, and washing by stirring up in water, and

allowing the finer particles to float off into a second vessel. Collect

this fine powder when sufficient has settled in the vessel and sift it

through a very fine sieve.

_Zinc-white cement_ is prepared similar to putty or red-lead cement.

It may, however, be made as follows: Mastic 2 parts, dammar 4 parts,

sandarac 6 parts, Venetian turpentine 8 parts, turpentine 10 parts,

benzole 12 parts, zinc white 14 parts.

The resins are powdered, while the Venetian turpentine, ordinary

turpentine, and benzole, are put in a bottle, and then the powdered

resins put in. The whole is shaken and allowed to stand for the resins

to dissolve. The solution is filtered through cotton-wool and rubbed

up with sufficient zinc-white to form a cement. Dilute with benzine if

necessary.

_Mastic cement, mastic or pierres de mastic._ Under this name masses

are brought into commerce which are well adapted for moulding

ornaments, such as figures, columns, etc., to be exposed to the

weather. They are comparatively cheap, and it is rather remarkable that

they are not more generally known and used for technical purposes.

To prepare large quantities of this cement suitable mills and mixing

vessels are required, as the conversion of the materials into a

dust-like flour is an indispensable condition of the success of the

work. The materials most generally used are fine quartz sand, finely

ground calcareous sand, and varying quantities of litharge or zinc

oxides, besides as small a quantity of linseed oil as possible.

The linseed oil combines with the litharge or zinc oxide to an

insoluble soap, which incloses the other material and forms a mass

acquiring the hardness of sandstone in thirty to fifty hours.

After converting the materials into a fine powder, the mixing is

accomplished in barrels filled about three-quarters full and revolved

by water-power. When a thorough mixture has been effected the

pulverulent mass is placed in sheet-iron vessels and saturated with

linseed oil, and then moulded at once, as it solidifies in one or two

days.

_French mastic._ Quartz sand 300 parts, pulverized limestone 100,

litharge 50, linseed oil 35.

_Paget’s mastic._ Sand 315 parts, whiting 105, white lead 25, calcined

red lead 10, lead acetate solution 45, linseed oil 35.

The mastic may be colored by adding pigments.

_Water-proof cement._ _A._ Rubber 7 parts, oil of turpentine 140,

linseed oil 40. _B._ Turpentine 100 parts, sulphuric acid 3, zinc-white

10.

To prepare solution _A_, place the rubber in the oil of turpentine in a

bottle. It swells very much without actually dissolving. After adding

the linseed oil, reduce the entire mass by boiling to one-half the

volume originally occupied by it.

Solution _B_ is prepared by stirring the sulphuric acid into the

turpentine and allowing it to stand for twelve hours. To remove the

sulphuric acid, the thick mass which has been formed is then kneaded in

water in which the zinc oxide has been distributed. After drying, the

resulting mass is dissolved in the warm fluid _A_.

_Another formula_ is as follows: Linseed oil 8 parts, litharge 12,

burnt lime 88.

Boil the linseed oil and litharge half an hour, then stir the lime into

the hot mass, and use the mixture hot. This cement is excellent for

filling in joints between stones, for flat roofs, water reservoirs,

etc. For a better adhesion of the cement, apply a coat of linseed

oil varnish to the surfaces to be cemented. Porous stones are made

water-proof by heating the cement in a boiler and adding sufficient

linseed oil to form a mass which can be readily worked with a smoothing

board. Apply as hot as possible.

_Serbat’s mastic._ Pyrolusite 60 parts, sulphate of lead 60, linseed

oil 10.

After thoroughly drying the materials, mix the sulphate of lead with

the linseed oil, then add 20 parts of the pyrolusite and, after mixing

and working it thoroughly, add gradually the rest of the pyrolusite in

small portions and kneading constantly.

_Stephenson’s oil cement._ Litharge 20 parts, unslaked lime 10 parts,

sand 10 parts, hot linseed oil 3 parts.

_Alum cement._ Dissolve good hard soap, by heating in rain water,

dilute the thickly fluid mass and add saturated alum solution as

long as a precipitate is formed. Collect the gelatinous precipitate

of alumina soap thus formed upon a cloth, and, after draining, pour

rain water over it ten to twelve times to remove the salts as much as

possible. After washing, dry the alumina soap, and rub it to a fine

powder.

To prepare cement rub a portion of the powder with sufficient

linseed-oil varnish to form a plastic dough, which is used for filling

in the joints.

This cement is water-proof, resists high temperatures without being

absolutely fire-proof, and, on account of its light color, is well

adapted for joining marble plates, etc.

_Oil cement for glass._ Litharge 30 parts, burnt lime 20, pipe-clay 10,

linseed-oil varnish 6.

_Oil cement free from lead for steam pipes._ Graphite 12 parts, heavy

spar 16, slaked lime 6, boiled linseed oil 6.

_Oil cements for steam pipes._ I. Litharge 25 parts, air-slaked lime

10, quartz sand 10.

Mix the ingredients quickly with the linseed oil and work the mass

thoroughly in a hot mortar. Coat the defective places in the pipes with

linseed-oil varnish, apply the cement hot and when partially solid,

make it still tighter by heating.

II. Boil 60 parts of graphite, 50 of air-slaked lime, 60 of elutriated

heavy spar in 35 of linseed oil, stirring constantly. Apply the mixture

hot.

_Oil cement for marble._ Elutriated litharge 10 parts, brick dust 100,

linseed oil 20.

Prepare in the same manner as glaziers’ putty. For various colors add

zinc white for white, red lead for red, pyrolusite for brown, etc.

Previous to applying the cement saturate the surfaces of the stones to

be cemented with linseed-oil varnish.

_Oil cement for porcelain._ Stir 20 parts of white lead and 12 of white

pipe-clay into 10 of boiling linseed oil previously boiled and knead

the mass thoroughly. After cementing let the articles stand quietly for

several weeks.

_Diamond cement._ Litharge 30 parts, air-slaked lime 10, whiting 20,

graphite 100, linseed oil 40. Apply hot. This is an excellent cement

for metal.

_Hager’s diamond cement._ Whiting 16 parts, elutriated graphite 50,

litharge 16.

Mix the pulverized ingredients with sufficient old, thick linseed oil

to form a plastic dough.

RESINOUS CEMENTS.

_Resinous cement for amber_ is obtained by melting mastic in linseed

oil. Volatile copal lacquer can also be advantageously used for the

purpose.

_Cement for turners._ Melt 1 lb. of rosin in a tin can over the fire,

and when melted add 4 ozs. of pitch; while these are boiling add brick

dust until, by dropping a little on a cold stone, you think it is hard

enough. In winter it may be found necessary to add a little tallow.

By means of this cement a piece of wood may be fastened to the chuck,

which will hold when cool, and when the work is finished, it may be

removed by a smart blow with the tool. All traces of the cement may be

removed from the work by repeated applications of benzine. To use this

cement, chip off as much as will cover the chuck to the 1/16th of an

inch, spread it over the surface in small pieces, mixing it with ⅛ of

its bulk of gutta-percha, then heat an iron to a dull red heat, and

hold it over the chuck till the mixture and gutta-percha are melted and

liquid. Stir the cement until it is homogeneous, chuck the work, lay

on a weight to enforce contact, leave it at rest 20 minutes.

The following cement is much employed and serviceable for the use of

turners and artisans in general.

Reduce 1 lb. of whiting to a fine powder, and heat to redness so as to

expel all the water. When cold this is mixed with 1 lb. of black rosin

and 1 oz. of beeswax previously melted together, and the whole stirred

till of uniform consistence.

_Cement for ivory and bone._ Melt at a moderate heat equal parts of

white wax, rosin, and oil of turpentine to form a thickly-fluid mass.

For coloring the cement add elutriated red lead, ultramarine, etc.

_Cement for white enameled clock-faces._ Dammar resin 100 parts, copal

100, Venice turpentine 110, zinc white 60, ultramarine 3.

Apply hot and polish when cold and hard.

_Cements for glass._ 1. Melt carefully 60 parts of bleached shellac and

10 of turpentine. If too thick, dilute with turpentine.

2. Shellac 20 parts, elemi 5, turpentine 10. Prepare as above.

_Cement for glass upon glass._ Shellac 10 parts, turpentine 2,

pulverized pumice stone 10.

_Cement for glass upon metal._ Melt together 40 parts of rosin, 20 of

rouge, 10 of wax, and 10 of turpentine. Apply hot to the surfaces to be

cemented.

_Cement for metal letters upon glass._ Rosin 42 parts, turpentine 4,

plaster of Paris 5.

_Cement for wood._ 100 parts of shellac and 45 of strong spirit of wine.

This cement serves for joining wood, which, on account of exposure to

water, cannot be glued. Apply the cement to the surface of one of the

pieces, and after placing upon it a piece of tissue paper press upon it

the other piece of wood previously coated with the cement.

_Cement for knife handles._ Melt together 20 parts of rosin, 5 of

sulphur, and 8 of iron filings.

Pour some of the hot mixture into the handle, and then push in the

knife previously heated.

_Cement for petroleum lamps._ Boil 12 parts of rosin in 16 of strong

lye until it is entirely dissolved and on cooling forms a tenacious

solid mass. Dilute this with 20 parts of water, and carefully work into

it 20 parts of plaster of Paris. This cement is insoluble in petroleum,

and is especially adapted for cementing the glass parts of lamps to the

metal. It is also a good material for stoppers for petroleum bottles.

_Cement for porcelain._ Rosin, 14 parts; elemi, 7; shellac, 7; mastic,

7; sulphur, 42; brick dust, 20.

_Cement for porcelain which is to be heated._ Heat carefully 10 parts

of amber in a large spoon, stirring constantly, until it evolves heavy

vapors of a strong odor. Rub the melted mass as finely as possible,

and after placing the powder in a bottle pour over it a mixture of

bisulphide of carbon and benzine. Close the bottle air-tight to

prevent the evaporation of the very volatile solvent. When the powder

is dissolved remove the cork and replace it by one provided with a

small brush. The application of the cement and pressing together of

the parts to be cemented must be effected as quickly as possible.

In articles properly cemented the joint can only be detected by the

closest examination. This cement holds so well that cups and saucers,

soup-tureens, etc., mended with it can be used for years.

_Cement to withstand the action of petroleum._ Dissolve 5 parts of

shellac, 1 of turpentine in 15 of petroleum. This cement is quite

elastic.

_Cement for mica._ A colored cement for joining sheets of mica is

prepared as follows: Soak clean gelatine in water, and when swelled

squeeze out the excess of water by pressure between a cloth, then melt

the gelatine by the heat of a water-bath, and stir in just enough proof

spirit to make it fluid. To each part of this solution add, while

stirring, ¼ oz. of gum ammoniac and 1½ ozs. of gum mastic dissolved in

4 ozs. of rectified alcohol. Put the mixture into bottles, and when

required for use stand the bottle in hot water. This cement resists

cold water.

_Cement for horn, whalebone and tortoise shell._ Dissolve gum mastic 10

parts and turpentine 4, in 12 of linseed oil. Apply hot.

_Cement for terra-cotta articles._ Melt together 70 parts of rosin,

70 of wax and 16 of sulphur, and stir into the mass 8 parts of hammer

slag and 8 of quartz sand. Coat the fractured surfaces with oil of

turpentine, apply the cement as quickly as possible, and press the

surfaces together. It is advisable to heat the terra cotta previously

to 158° or 176° F. After cementing the article, smooth the joint with a

heated knife and dust very fine terra-cotta powder through a linen bag

upon the soft cement in order to give it exactly the same color as the

article itself.

_Mastic cement for glass._ Gum mastic 15 parts, bleached shellac 10,

turpentine 5.

This mass sufficiently diluted with hot oil of turpentine furnishes

an excellent cement for fractured glass and gems. Being colorless,

the joint can scarcely be detected, provided the cementing has been

skilfully done.

To attach gems to glass of the same color, the cement is colored with

aniline colors dissolved in spirit of wine, care being had to give it

the same shade as the gem and the glass.

_Stick mastic cement._ Melt together, at as low a temperature as

possible, 10 parts of mastic and one of turpentine, and pour the mass

into suitable moulds.

For use, heat the fractured surfaces of the article strongly, so that

the cement on being rubbed over them melts, then press the surfaces

together and continue the pressure until the cement solidifies.

_Sulphur cement for porcelain._ White pitch 18 parts, sulphur 28,

bleached shellac 4, gum mastic 8, elemi 8, glass meal 28. Melt all

together, except the glass meal and stir the latter into the melted

mass.

_Insoluble cement for wooden vessels._ Melt together 60 parts of rosin,

20 of asphalt, and 40 of brick dust. Pour the hot mixture into the

joints. This cement resists the action of lye, quick lime, sulphuric

and hydrochloric acids.

RUBBER CEMENTS.

These cements are very useful, but owing to the inflammable nature of

the components, great care should be taken to guard against fire while

preparing them. They should never be made near a naked fire, as the

benzine, carbon disulphide or chloroform used to dissolve the rubber is

very volatile, and the vapor given off permeates the air until, coming

near a source of light, the whole air becomes one vivid sheet of flame.

Vessels which are used should be closed, and if possible put out of

doors. If heat is required to assist the solvent action, use a sand or

hot-water bath, but on no account bring near a fire.

_Cements for glass._ I. Rubber 1 part, gum mastic 12, dammar 4,

chloroform 50, benzine 10.

II. Rubber 12 parts, chloroform 500, gum mastic 120.

This cement adheres immediately, and possesses a high degree of

elasticity. It may be used to advantage for joining together the glass

panes of hot-houses.

III. Dissolve, without application of heat, rubber 2 parts and gum

mastic 6, in 100 of chloroform. This cement is perfectly transparent.

It should be applied as quickly as possible, as it sets in a very short

time.

_Soft rubber cement._ Melt 10 parts of tallow in a brass pan and

gradually add 150 parts of rubber in small pieces, and stir constantly

until all the rubber is dissolved. Keep in readiness a well-fitting

lid to be able to extinguish the flame immediately in case the rubber

catches fire. When all is melted stir in 10 parts of slaked lime.

This cement is especially adapted for sealing bottles containing

caustic substances, such as nitric acid, etc. It remains always

tenacious, being therefore suitable for cementing bodies exposed to

repeated shocks.

_Hard rubber cement._ Rubber, 150 parts; tallow, 10; red lead, 10.

This cement is prepared in the same manner as the above. The addition

of red lead gives it a red color, and solidifies it in a short time to

a mass as hard as stone.

_Elastic cement._ Carbon disulphide, 8 ozs.; fine rubber, 1 oz.;

isinglass, 4 drachms; gutta-percha, 1 oz. Dissolve the solids in the

fluid.

This cement is used for cementing leather and rubber. For use the

leather is roughened and a thin coat of the cement applied and allowed

to dry completely; then the two surfaces to be joined are warmed and

placed together and allowed to dry.

_Marine glue._ This cement, which is only a glue in name, is

water-proof, and can be used to cement metal, wood, glass, stone,

pasteboard, etc., and is especially adapted for caulking vessels.

Suspend 10 parts of rubber inclosed in a bag in a vessel containing 120

parts of refined petroleum, so that only half of the bag is immersed,

and allow it to remain ten to fourteen days in a warm place. Then melt

20 parts of asphalt in an iron boiler and add the rubber solution in a

thin jet, and heat the mixture, while constantly stirring, until it is

perfectly homogeneous. Pour it into greased metallic moulds, where it

forms into dark-brown or black plates difficult to break. In using it,

it should be melted in a kettle placed in boiling water to prevent its

burning, which it is very apt to do, as it is a bad conductor of heat.

After it has been liquefied remove the kettle from the water and place

it over a fire, where it can be heated, if necessary, to make it more

fluid, to 302° F., carefully stirring it to prevent burning.

If possible, the surfaces to be glued together should be heated to

212° F., as the glue can then be slowly applied. The thinner the layer

of glue in cementing together smooth surfaces, the better will it

adhere. But a somewhat thicker layer is required for rough surfaces,

for instance, boards not planed, the excess of glue being forced out by

strong pressure. Generally speaking, it is best to subject all articles

cemented together with marine glue to as strong a pressure as possible

until the glue is congealed.

Repeated experiments have shown that with the aid of this cement square

vats perfectly water-tight can be constructed of boards. Wooden pegs

dipped in the compound should be used for putting the vats together.

_Jeffrey’s marine glue._ Dissolve 1 part of rubber in benzine, and mix

the solution with 2 parts of shellac by the assistance of heat.

_Another formula_ is as follows: Coal naphtha 1 quart, rubber cut in

shreds 2 ozs. Macerate for 10 or 12 days and then rub smooth with a

spatula on a slab; add 2 parts by weight of shellac to 1 part of this

solution. To use the compound melt it at about 240° F.

_Marine glue for damp walls._ Rubber 10 parts, whiting 10, oil of

turpentine 20, carbon disulphide 10, rosin 5 and asphalt 5. Dissolve

the ingredients in a suitable vessel and stand in a warm place, shaking

it frequently.

Scrape the wall smooth and clean, and apply the glue with a broad brush

on the damp place and about 8 inches higher than the line of dampness.

Before the glue is dry lay on plain paper which will adhere tightly. On

this plain paper the wall paper can be pasted in the usual manner. If

carefully done, the wall paper will always remain dry.

GUTTA-PERCHA CEMENTS.

_Cement for leather._ Gutta-percha 100 parts, pitch or asphalt 100, oil

of turpentine 15.

This cement should be used hot. It is suitable for cementing all kinds

of substances, but adheres particularly well to leather.

_Cement for hard rubber combs._ _A._ Prepare a very thick solution of

bleached gutta-percha in bisulphide of carbon.

_B._ Dissolve sulphur in bisulphide of carbon.

The cementing is effected by applying solution _A_ to the fractured

surfaces and pressing them together. When dry brush solution _B_ over

the cemented place.

_Elastic gutta-percha cement._ Dissolve 10 parts of gutta-percha in 100

of benzine, then pour the clear solution into a bottle containing 100

parts of linseed-oil varnish and unite both by shaking. This cement

excels in elasticity, and is especially suitable for attaching the

soles of shoes, as it is so elastic that it will not break, no matter

how much it is bent. To make it adhere tightly roughen the leather on

the side to be cemented.

_Cement for horses’ hoofs._ For filling cracks and fissures in horses’

hoofs a cement is required which possesses great resistance to the

action of water combined with elasticity and solidity. A mass answering

all demands consists of 10 parts by weight of gum ammoniac and 20 to

25 of purified gutta-percha. Heat the gutta-percha to between 194°

and 212° F., and then work it with the finely powdered gum ammoniac

to a homogeneous mass. In using it, soften the cement by heating, and

after carefully cleansing the crack in the hoof, apply it with a heated

knife. The cement solidifies immediately after cooling to the ordinary

temperature, and becomes soon so hard as to allow of nails being driven

into it.

_Cement for crockery._ Gutta-percha 1 part, shellac 1.

Place the two ingredients in an earthenware jar, and melt the two

together by standing this jar on a vessel of boiling water, or else one

filled with hot sand, the vessel holding the water or sand being heated

over a fire or gas furnace. Stir the melted ingredients well together.

The resulting cement is one possessing great hardness and toughness,

which suits it admirably for mending crockery. Warm the edges to be

joined together, smear the cement on, join together, and hold the

article thus joined until cool.

_Cement for leather._ Mix 10 parts of carbon disulphide with 1 part

of turpentine, and then add sufficient gutta percha to make a tough,

thickly-fluid mass. Before using this cement, free the surface to be

joined from grease. To effect this, sprinkle a little bicarbonate of

soda, carbonate of ammonia or borax on the surfaces to be joined, lay

a cloth over them, and then place a hot iron on top, and keep it there

a short time so as to cause the alkali to cut the grease, then put the

cement on both surfaces to be joined, put them together and subject to

pressure until they are cemented.

Gutta percha dissolved in carbon disulphide to the consistency of syrup

is also a good cement for joining leather. The parts to be joined

should be well covered with cement so as to fill the pores of the

leather, then the cement is heated and the parts hammered until the

cement is cold.

CASEINE CEMENTS.

_Preparation of pure caseine._ Although the caseine contained in old

cheese can be used, the other constituents, such as fat, salt, and free

acid, exert an injurious influence upon the solidity of the cement

prepared with it. It is, therefore, best to prepare pure caseine, which

is easily accomplished in the following manner:

Put milk in a cool place, and after taking off the cream as long as any

is formed, remove the skimmed milk to a warm place to coagulate. After

heating the curd, place it upon a filter and wash the caseine remaining

upon the filter with rainwater until the water running off shows no

trace of acid.

To remove the last traces of fat tie the washed caseine in a cloth and

after boiling it in water, spread it upon blotting paper in a warm

place to dry. It will shrivel up to a horny mass.

When thoroughly dried pure caseine will keep for a long time without

suffering alteration. To obtain the caseine in a form suitable

for preparing cements it is only necessary to pour water over a

corresponding quantity and allow it to stand for some time. Caseine

combines with lime to a hard insoluble mass.

Ordinary technical caseine may be readily and cheaply prepared as

follows: Skim milk is heated in a copper boiler, if necessary by the

introduction of steam, to 122° F. Then add for every 1000 quarts of

milk, 3 quarts of crude hydrochloric acid diluted with 5 to 6 times

the quantity of water. After coagulation, the whey is drained off, the

curd spread out upon an inclined table and allowed to cool. The curd is

then washed by pouring cold water over it through a rose, or stirring

it up with water in a barrel, allowing to settle, and pouring off the

supernatant water. The residue is subjected to moderate pressure. The

caseine while still moist is comminuted in a curd-mill and packed in

bags. In this state it must be worked at once, as otherwise it spoils

readily and is attacked by worms. If it is to be kept for a longer

time, it has to be dried. This is effected by spreading it out upon

linen cloths and placing it in a drying chamber.

In this manner 8.5 per cent. of moist, or 3.5 per cent. of dry, caseine

is obtained which is brought into commerce as technical caseine or

lactarine. It being insoluble in water, 10 per cent. of an alkali—soda,

borax, or ammonia—has to be added to effect solution. Water-soluble

caseine is seldom found in commerce, the consumer preparing it, as a

rule, himself.

A purer technical caseine is obtained according to John A. Just’s

method as follows: Dissolve, stirring constantly, in 115 quarts of

water heated to between 104° and 131° F., 17 to 26 ozs. of bicarbonate

of soda and 176 lbs. of moist, or 118 lbs. of dry, caseine, and dry the

solution upon a heated revolving metal cylinder. After each revolution

of the cylinder, the dry material is scraped off with brushes and by

being forced through a fine-meshed sieve yields soluble caseine powder.

_Caseine cement which can be kept for a long time._ Convert into

powder, each by itself, 200 parts of caseine, 40 of burned lime, and

1 of camphor. Mix the powders intimately and keep the mixture in an

air-tight bottle. For use, mix some of the powder with the requisite

quantity of water and use the cement at once.

_Cement for glass._ Old dry cheese 100 parts, water 50, slaked lime 20.

Free the cheese from rind, and rub it with the water until a

homogeneous mass drawing threads is formed. Then stir in quickly the

lime powder, and use the cement at once. It unites not only glass to

glass, but can also be used for cementing metal to glass.

_Cement for metals._ Elutriated quartz sand, 10 parts; caseine, 8;

slaked lime, 10, and sufficient water to form a cream-like mass.

_Cement for porcelain._ Caseine dissolves readily in solution of

water-glass, and forms then one of the best cements for porcelain

known. To prepare it, fill a bottle one-quarter full with fresh

caseine, and after filling the bottle with solution of water-glass,

effect the solution of the caseine by frequent shaking.

_Cement for meerschaum._ Dissolve caseine in water-glass, and after

stirring quickly finely-pulverized calcined magnesia into the mass, use

it at once, as it solidifies very soon. By adding, besides magnesia,

genuine meerschaum finely pulverized, a mass closely resembling

meerschaum is obtained, which can be used for manufacturing imitation

meerschaum.

_Cement for wood, etc._ Rub 10 parts of caseine and 5 of borax

to a thick, milky mass, and use it like glue. This cement can be

advantageously used for pasting labels upon wine bottles, as it neither

moulds nor becomes detached in the cellar.

_Another formula_ is as follows: Dissolve borax by boiling in water,

and pour the solution over fresh caseine. The result will be a clear,

thick mass of extraordinary power of adhesion, which can be kept for

any length of time without suffering decomposition.

Applied to leather, paper, linen or cotton goods, it forms a coat of

beautiful lustre, and for this reason is much used in the manufacture

of fancy articles of paper and leather.

_Cement for porcelain._ Dissolve 10 parts of caseine in 60 of

water-glass solution. Apply the cement quickly and dry the cemented

articles in the air.

WATER-GLASS AND WATER-GLASS CEMENTS.

_Water-glass._ Water-glass (silicate of soda or soluble glass) is

found in commerce as a thickly-fluid, tenacious mass. It is generally

prepared by fusing 15 parts of quartz sand with 8 of carbonate of

soda and 1 of charcoal. The silicic acid combining with the soda

disengages the carbonic acid, the expulsion of which is facilitated by

the presence of charcoal, which converts it into carbonic oxide. It

dissolves readily in water. The solution has a strongly alkaline taste,

and possesses the property of being gradually converted, on exposure to

the air, to a gelatinous mass which finally solidifies. For this reason

water-glass should be kept in bottles hermetically closed with corks.

Glass stoppers are of no use, as they are so firmly cemented to the

bottle that on attempting to open the latter the neck breaks off.

By combining water-glass with cement or burned lime the resulting mass

solidifies quite rapidly to a mass as hard as stone, and generally

capable of resisting chemical action.

Water-glass by itself is only fit for cementing glass to glass, but

combined with other substances it furnishes very durable and solid

cements.

_Cement for cracked bottles._ Select a cork which will fit the bottle

air-tight and place it loosely upon the bottle, and heat the latter

gradually to at least 212° F. Then press the cork down and apply a

thick solution of water-glass to the cracks. In cooling, the air in the

bottle contracts strongly, and the pressure of the exterior air drives

the water-glass with great force into the cracks closing them entirely

so that they cannot be detected.

_Cement for glass and porcelain._ Stir quickly together 10 parts of

elutriated glass meal, 20 of powdered fluor spar, and 60 of water-glass

solution, and apply the homogeneous paste at once. In a few days the

cement will be so hard that the cemented vessels can be heated without

danger.

_Cement for hydraulic works._ Finely powdered cement, and solution of

water-glass. Mix the two bodies quickly together.

As this cement hardens very quickly, it should be used fresh. It

hardens under water, and is therefore excellent for hydraulic works.

The stones should be coated with a solution of water-glass before

applying the cement.

_Cement for uniting metals._ A strong cement, which hardens rapidly, is

made by stirring the finest whiting in a solution of soda-glass of 33°

B., made so as to form a plastic mass. This can be readily colored to

any desired shade. The addition of sifted sulphide of antimony gives

a black cement, which by polishing acquires a metallic lustre; iron

filings render it grayish-black; zinc dust turns it green, but after

polishing, it appears like metallic zinc, and may be employed for the

permanent repair of zinc ornaments, etc. Carbonate of copper imparts a

light green shade. Other additions may be made, as oxide of chrome for

dark green, cobalt blue for blue, red lead for orange, vermilion for

scarlet, carmine for violet, etc.

_Cement for tightening joints of pipes exposed to a red heat._ Mix 80

parts of pyrolusite, 100 of zinc white, and 20 of water-glass.

This cement fuses at a temperature not too high, and then forms a

glass-like mass which adheres very firmly and closely.

_Cement for marble and alabaster._ The point of fracture of articles

cemented with the following mixture is difficult to find, and the

cemented place is much stronger than the material itself. Mix 12

parts of Portland cement, 6 of slaked lime, 6 of fine sand, and 1 of

infusorial earth with sufficient water-glass to form a thick paste. The

article to be cemented need not be heated. It hardens in twenty-four

hours.

GLYCERINE AND GLYCERINE CEMENTS.

Commercial glycerine is a yellowish or nearly colorless and more or

less viscid liquid having an intensely sweet taste. In combination with

lead oxide and intimately worked into it, by heating and stamping,

it furnishes very strong and durable cements deserving general

introduction, though thus far they have been but little used.

For the manufacture of cements the use of pure odorless glycerine

is not required, the yellow crude article, which is much cheaper,

answering all purposes. The principal point is to use very highly

concentrated glycerine, as otherwise the cements prepared with it

solidify very slowly and besides do not possess a proper degree of

hardness and solidity.

It is of especial importance to have the lead oxide free from water. To

accomplish this, heat it thoroughly and mix it with the glycerine while

still hot. Cement thus prepared solidifies very quickly, and can be

used for many purposes. It is an excellent material for quickly joining

the stones of submarine works.

_Glycerine and litharge cement._ Moisten elutriated litharge with

glycerine so that a thin homogeneous paste is formed. This cement is

adapted for uniting the joints of steam pipes, cementing wood, glass,

porcelain, and also glass upon metal, etc. It solidifies to a very hard

mass in a quarter to three-quarters of an hour. Before applying the

cement coat the surfaces to be joined with pure glycerine.

LIME CEMENTS.

Quick lime, slaked lime and chalk are used for this purpose. Quick

lime, which is obtained by burning limestone, combines gradually with

the fats to insoluble lime soaps. Slaked lime, which consists of a

combination of lime with water, acts in the same manner.

For the preparation of cements the lime is slaked by placing it in a

dish and pouring as much water over it as it will absorb. Good lime,

technically called _fat lime_, should eagerly combine with water,

evolving much heat, swelling greatly, and crumbling to a light white

powder.

Quick lime exposed to the air until, by the absorption of moisture and

carbonic acid, it is converted into a powder is called _air-slaked_.

Cements prepared with quick lime will, as a rule, solidify more quickly

than those prepared with air-slaked lime.

Chalk is a carbonate of lime consisting of the shells of microscopic

animals, and can be readily pulverized and elutriated. In the latter

state it is known as _whiting_. For the preparation of entirely white

cements the use of pure white lime or chalk is absolutely necessary.

Yellow or reddish lime contains oxide of iron, and furnishes cements of

the same tinge.

_Cement for glass._ Litharge 30 parts, quick lime 20, linseed-oil

varnish 5.

_Cement for joiners._ A cement for filling up cracks and holes is

obtained by mixing slaked lime 50 parts, flour 100, linseed-oil varnish

15.

_Cement for cracked clay crucibles and porcelain._ By applying to the

cracks a mixture of 10 parts of slaked lime, 10 of borax, and 5 of

litharge in sufficient water to form a stiff paste, and drying after

heating the crucible, the cracked places will be united so firmly that

the crucible, when thrown to the ground, will generally break in any

other place than the cemented one.

This cement can also be used for porcelain capable of standing a strong

heat.

_Lime and glue cement._ Stir air-slaked lime into hot glue. This cement

is especially suitable for attaching metal to glass. It forms a very

hard yellowish-brown mass.

GYPSUM CEMENTS.

Sulphate of lime in combination with water is met with in nature, both

in the form of transparent prisms of _selenite_, and in opaque and

semi-opaque masses, known as _alabaster_ and _gypsum_. By pulverizing

the latter and heating to about 302° F. it loses its water, and is

converted into anhydrous gypsum or _plaster of Paris_, which on mixing

with water recombines with it to form a mass of hydrated sulphate of

lime, the hardness of which nearly equals that of the original gypsum.

When the powder is mixed with water to a cream and poured into a mould,

the minute particles of anhydrous sulphate of lime combine with the

water to reproduce the original gypsum, and this act of combination

is attended with a slight expansion which forces the plaster into the

finest lines of the mould.

By using a solution of alum instead of ordinary water, a plaster is

obtained which, although it takes much longer to set than the ordinary

kind, is much harder, and therefore takes a good polish.

For preparing cements only perfectly white plaster of Paris should be

used, as the gray article possesses but little adhesive power.

_Cement for plaster of Paris statues._ To repair plaster of Paris

statues so that the point of fracture cannot be detected, proceed in

the following manner:

Moisten the fractured surfaces with water by means of a brush until

they absorb no more and remain moist. Mix plaster of Paris with

water to a thin cream and stir until the heat appearing at first has

ceased, which will prevent the conversion of the plaster into a solid

coherent mass. Apply quickly a thin layer of the plaster to one of the

fractured surfaces, press the other against it until the plaster has

set, and, when dry, carefully remove the excess by scraping.

_Cement for glass and porcelain._ Mix quickly 50 parts of plaster of

Paris, 10 of quick lime, and 20 of white of egg. Use at once, as the

cement solidifies very rapidly.

_Cement for iron and stone._ A very useful cement for securing iron

railing in stone is obtained by mixing 30 parts of plaster of Paris, 10

of iron filings and 20 of vinegar.

_Cements for porcelain._ I. Mix plaster of Paris with saturated

solution of alum to a cream. After moistening the fractured surfaces

apply a thin layer of the cement, press the surfaces together, wrap a

wire or cord tightly around them, and let the article stand quietly for

a few weeks. The cement is converted into a mass as hard as stone.

II. Mix plaster of Paris with a thick, clear solution of gum arabic and

cement the articles as soon as possible. Although this cement adheres

very tightly, porcelain vessels cemented with it cannot be used for

liquids.

_Universal plaster of Paris cement._ Mix 21 parts of plaster of Paris,

3 of iron filings, 10 of water, and 4 of white of egg. This cement is

suitable for attaching metal to glass, metal to stone, etc.

IRON CEMENTS.

_Heat-resisting cement._ Clay 10 parts, iron filings 5, vinegar 2,

water 3.

_Water and steam-proof cement._ Iron filings 100 parts, sal-ammoniac 2,

water 10.

This cement rusts very much in a few days, and is converted into an

extremely solid mass which is perfectly steam- and water-proof.

_Cement for iron._ Mix 65 parts of wrought-iron filings, 2.5 of sal

ammoniac, and 1.5 of flowers of sulphur, and then add 1 part of

sulphuric acid diluted with sufficient water to form a stiff paste.

This cement solidifies in two to three days, and rusts, with the parts

of iron to be cemented, to an extraordinarily durable mass.

_Fire-proof cement for iron pipes._ Wrought-iron filings 45 parts, clay

20, fire-clay 15, common salt solution 8.

_Cements resisting high temperatures._ 1. Iron filings 20 parts, clay

powder 45, borax 5, common salt 5, pyrolusite 10.

Dissolve the borax and common salt in the water, add and mix quickly

the clay powder, pyrolusite, and iron filings. Apply the cement at

once. Exposed to a white heat, it hardens to a tightly adhering, glassy

mass.

2. Mix 52 parts of pyrolusite, 25 of zinc white, and 5 of borax with

solution of water-glass to a paste, and use at once. This cement

requires to be gradually dried. It will stand the highest temperatures.

_Cement for filling in defects in castings._ Stir 100 parts of iron

filings free from rust with sufficient water to form a thick paste, and

press the mixture into the fissures, cracks, etc. The cement becomes

solid only after the iron filings become strongly rusted. To free the

ingredients from adhering fat, wash them, before mixing, in liquid

ammonia.

_Cement for cracked stove plates, etc._ Knead 20 parts of iron filings,

12 of iron scale, 30 of plaster of Paris, and 10 of common salt with

blood to a stiff paste, and use at once. Instead of blood, water-glass

can be used, it having the advantage of being odorless on strong

heating, while blood cement evolves a disagreeable odor.

_Cement for iron water tanks._ Knead iron filings with vinegar to

paste. Allow the mixture to stand until it turns brown, and then force

it into the joints by means of a chisel.

_Cement for cracked iron pots._ Knead 10 parts of iron filings and

60 of clay with linseed oil to a thick paste. Before applying it add

a little linseed oil, and allow it to dry slowly. In a few weeks the

cement will be so hard that the vessels can be used without danger.

_Black cement for stoves._ Iron filings 10 parts, sand 12, bone black

10, slaked lime 12, glue water 5.

_Cements for iron stoves._ 1. Pulverize as finely as possible and mix

intimately 4 to 5 parts of clay, 2 of iron filings free from rust, 1 of

pyrolusite, ½ of common salt, and ½ of borax with water to a paste, and

apply the cement quickly to the places to be cemented and allow it to

dry slowly. This cement will stand a white heat, and resist the action

of boiling water.

2. Mix intimately and as quickly as possible 1 part of pulverized

pyrolusite, and 1 of zinc white with solution of water-glass to a

plastic mass, which solidifies quickly. The power of resistance of this

cement, it is claimed, is not inferior to No. 1, though experiments

have proved No. 1 to be preferable.

CEMENTS FOR CHEMICAL APPARATUS.

Cements to be used for the above purpose must possess various

properties difficult to combine in one preparation. They must be

gas-proof, and capable of resisting the action of different vapors and

acid fluids. As regards resistance to the action of chemical agents,

there is nothing better than caoutchouc, but unfortunately it can

only be used for tightening chemical apparatus not exposed to a high

temperature.

In chemical laboratories bran of almonds, either by itself or kneaded

with water to a thick paste, is frequently used, or rye or wheat

bran mixed with a little flour and water. These cements, though very

suitable for cementing glass distilling apparatus, are strongly acted

upon by chlorine and the vapors of nitric acid.

For small apparatus to be used for the development of fluoric acid,

plaster of Paris mixed with a little water can be used as a cement.

To make the joint entirely gas-tight, paste a strip of paper over it.

Although this cement does not resist the action of fluoric acid for

any length of time, it suffices generally for the protection of the

Workmen during the time the development of the acid is in progress, as,

for instance, in chemical analyses, etc.

To cement chemical apparatus exposed to a temperature not exceeding 86°

to 104° F. paraffine does excellent service; as it possesses the power

of resisting the action of the strongest acids and alkalies.

Below will be found a few receipts for cements which have proved

reliable.

_Linseed oil and clay cement._ Knead 10 parts of dry clay with 1 of

linseed oil to a homogeneous mass. This cement will stand heating to

the boiling-point of mercury.

_Linseed oil, zinc and manganese cement._ Knead 10 parts of pyrolusite,

20 of zinc white, and 40 of clay with sufficient boiled linseed oil

(not exceeding 7 parts) to a plastic mass. This cement will stand a

somewhat higher temperature than the preceding one.

_Cements resisting very high temperatures._ I. Clay 100 parts, powdered

glass 2.

The glass melts on exposure to great heat and slags the clay to a hard

mass. The same effect is produced by adding small quantities of soda

and borax to the clay. An admixture of chalk and boric acid, as in the

following receipt, also gives excellent results.

II. Clay 100 parts, chalk 2, boric acid 3.

_Cement resisting acids._ Melt rubber with double the quantity of

linseed oil, and then knead in sufficient bole to form a paste. This

cement resists the action of nitric and hydrochloric acids, and can

be advantageously used for closing bottles containing them. As it

solidifies very slowly, it can readily be detached from the bottles,

and used again.

For cement which is to solidify quickly on exposure to the air, add a

few per cent. by weight of red lead or litharge.

_Rubber cement for chemical apparatus._ Cut 8 parts of rubber in small

pieces and throw them gradually into a mixture of 2 parts of tallow

and 16 of linseed oil previously strongly heated. After effecting an

intimate mixture of the constituents by vigorous and constant stirring,

add 3 parts of white bole.

Although this cement does not stand a high temperature, it possesses an

extraordinary power of resisting the action of acid vapors.

_Scheibler’s cement for chemical apparatus._ Melt together 1 part of

wax and 3 of shellac, and work into the mixture 2 parts of gutta-percha

cut up in very small pieces. This cement will bear considerable heat

without actually melting.

CEMENTS FOR SPECIAL PURPOSES.

_Cement for attaching metal letters to glass, marble, wood, etc._

Dissolve over a water-bath 5 parts of glue in a mixture of 15 parts

of copal varnish, 5 parts of boiled linseed oil, 3 parts of crude oil

of turpentine, and 2 parts of rectified oil of turpentine, and add 10

parts of slaked lime to the mixture.

_Cement for joints of iron pipes._ Mix 5 lbs. of coarsely powdered iron

borings, 2 ozs. of powdered sal ammoniac, and 1 oz. of sulphur with

sufficient water to form a paste. This composition hardens rapidly, but

if time can be allowed it sets more firmly without the sulphur. It must

be used as soon as mixed, and rammed tightly into the joint.

Another receipt is as follows:

Mix 2 ozs. of sal ammoniac, 1 oz. of sublimated sulphur and 1 lb. of

cast-iron filings or fine turnings in a mortar, and keep the powder

dry. When it is to be used, mix it with 20 times its weight of clean

iron turnings or filings and grind the whole in a mortar; then wet it

with water until it becomes of convenient consistency, when it is to be

applied to the joint. After a time it becomes as hard and strong as the

metal.

_Steam boiler cement._ Mix 10 parts of finely-powdered litharge with

1 part of fine sand and 1 part of air-slaked lime. The mixture may be

kept for any length of time without deterioration. For use a portion

of it is made into a paste with linseed oil or, better, boiled linseed

oil. In this state it must be applied quickly, as it soon becomes hard.

_Cement for rubber._ Powdered shellac is softened in 10 times its

weight of strong water of ammonia, whereby a transparent mass is

obtained, which becomes fluid after keeping some little time without

the use of hot water. In three to four weeks the mixture is perfectly

liquid, and when applied it will be found to soften the rubber. As soon

as the ammonia evaporates it hardens again, and thus becomes impervious

both to gases and to liquids. For cementing sheet rubber, or rubber

material in any shape, to metal, glass, and other smooth surfaces, this

cement is highly recommended.

_Cement for tires._ 1. Isinglass 1 oz., gutta-percha 1 oz., rubber 2

ozs., carbon disulphide 8 fluid ozs. Mix and dissolve.

2. Shellac 4 ozs., gutta-percha 4 ozs., red lead and sulphur, each ½

oz. Melt the shellac and gutta-percha, and add with constant stirring

the red lead and sulphur, melted. Use while hot.

3. Crude rubber 1 oz., carbon disulphide 8 ozs. Macerate 24 hours, and

then add a solution of:

Rosin 2 ozs., beeswax ½ oz., carbon disulphide 8 ozs.

4. Rubber 20 parts, rosin 10, Venetian red 10, tallow 5. Melt the

rubber over a fire, then add the rosin and the tallow and finally the

Venetian red.

_Cement for steam pipes, etc._ A cement of specially valuable

properties for steam pipes, in filling up small leaks, such as a

blow-hole in a casting, without the necessity of removing the injured

piece, is composed of 5 lbs. Paris white and 5 lbs. yellow ochre, 10

lbs. litharge, 5 lbs. red lead and 4 lbs. black oxide of manganese.

Mix the materials thoroughly and make into a paste with a small

quantity of asbestos and boiled linseed oil. The composition, as thus

prepared, will harden in from 2 to 5 hours, and has the advantage of

not being subject to expansion and contraction to such an extent as to

cause a leakage afterwards, and its efficiency in places difficult of

access is of special importance.

_Cement for marble._ Stir to a thick batter with silicate of soda 12

parts of Portland cement, 6 of slaked lime, 6 of fine white lead and 1

of infusorial earth. This is excellent for marble and alabaster. The

cemented objects need to be heated. After 24 hours the fracture is

firm, and the place can scarcely be found.

_Cement for attaching wood, glass, etc., to metal._ Acetate of lead 23

parts by weight, alum 23, gum arabic 38, wheat flour 250.

Dissolve the acetate of lead and the alum in a little water and

separately dissolve the gum arabic in a fair quantity of boiling

water. Thus if the 250 parts of wheat flour represent half a pound,

the quantity of water needed will be about a pint. The gum having

dissolved, add the flour, put the whole on the fire, stir well with a

wooden stick, then add the solution of lead acetate and alum. Continue

the stirring in order to avoid the formation of lumps, then take it off

the fire without allowing it to boil. This cement is used cold, and

will not scale. It is very useful in making wood, glass, cardboard,

etc., adhere to metal, and is extremely strong.

_Brushmakers’ cement._ Rosin 5 lbs., rosin oil or spirit 1 quart.

Reduce the rosin to small pieces, run down in a pot, add the other

ingredient, and stir until mixed and syrupy, then run out into tins.

It is used for cementing the bristles in the stocks, also for string

binding on sash tools, etc.

_Cement for electrical apparatus._ Mix together 1 lb. of beeswax

added to 5 lbs. of rosin, 1 lb. of red ochre, and 2 tablespoonfuls of

plaster of Paris. It will make an excellent composition for electrical

apparatus.

A cheaper composition for cementing voltaic plates into wooden troughs

is made with 6 lbs. of plaster of Paris and ¼ pint of linseed oil. The

ochre and the plaster of Paris should be well dried and added to the

other ingredients when these are in a melted state.

_Jewelers’ cement._ Dissolve over the water-bath 25 parts of fish glue

in a small quantity of strong spirits of wine, add 2 parts of gum

ammoniac; separately dissolve 1 part of mastic in 5 of spirits of wine.

Mix the two solutions and keep them in well-stoppered bottles.

_American cement for jewelers._ Soak 4 ozs. of isinglass in 2 lbs. of

water for 24 hours, then evaporate in the water-bath; to 1 lb. add 1

lb. of rectified spirits of wine, and strain. Then mix in a solution

of 2 ozs. of mastic and 1 oz. of gum ammoniac in 16 ozs. of rectified

spirit.

_Cement for celluloid._ Shellac 2 ozs., spirits of camphor 2, 90 per

cent. alcohol 6 to 8.

_Stratena._ This well-known household cement is said to be prepared

as follows: Dissolve 12 parts of white glue in 16 of acetic acid, and

then add this solution to one of 2 parts gelatine in 16 of water. After

mixing add 2 parts shellac varnish.

_Cement for cloth._ Gutta-percha 16 parts, rubber 4, pitch 2, shellac

1, linseed oil 2 pints. Dissolve the whole by heat, stirring constantly.

HOW TO USE CEMENTS.

It is unquestionably true that quite as much depends upon the manner in

which a cement is applied, as upon the cement itself. The best cement

that was ever compounded would prove entirely worthless improperly

applied. In the foregoing a number of cements have been given which

answer every reasonable demand when properly prepared and properly

used. Good common glue will unite two pieces of wood so firmly that

the fibres will part from each other rather than from the cementing

material; two pieces of glass can be so joined that they will part

anywhere rather than on the line of union; glass can be united to

metal, metal to metal, stone to stone, and all so strongly that the

joint will certainly not be the weakest part of the resulting mass.

What are the rules to be observed in effecting these results?

The first point that demands attention is to bring the cement itself

into intimate contact with the surface to be united. If glue is

employed, the surface should be made so warm that the melted glue

will not be chilled before it has time to effect a thorough adhesion.

The same is more eminently true in regard to cements that are used

in a fused state, such as mixtures of resins, shellac, and similar

materials. These matters will not adhere to any substance unless the

latter has been heated to nearly or quite the fusing point of the

cement used. This fact was quite familiar to those who used sealing-wax

in the olden days of seals. When the seal was used, in succession,

rapidly so as to become heated, the sealing-wax stuck to it with

a firmness that was annoying, so much so that the impression was

generally destroyed, from the simple fact that the sealing-wax would

rather part in its own substance than at the point of adhesion to the

seal. Sealing-wax or ordinary so-called electric cement is a very good

agent for uniting metal to glass or stone, provided the masses to be

united are made so hot as to fuse the cement; but if the cement is

applied to them while they are cold, it will not stick at all. This

fact is well known to those itinerant venders of cement for uniting

earthenware. By heating two pieces of delf so that they will fuse

shellac, they are able to smear them with a little of this gum and

join them so that they will rather break at any other part than along

the line of union. But although people see the operation constantly

performed and buy liberally of the cement, it will be found that in

nine cases out of ten, the cement proves worthless in the hands of the

purchasers, simply because they do not know how to use it. They are

afraid to heat a delicate glass or porcelain vessel to a sufficient

degree, and they are apt to use too much of the material, and the

result is a failure.

The great obstacles to the junction of any two surfaces are air and

dirt. The former is universally present, while the latter is due to

accident or carelessness. All surfaces are covered with a thin adhering

layer of air, which it is difficult to remove, and which, although

it may at first sight seem improbable, bears a relation to the outer

surface of most bodies different from that maintained by the air a few

lines away. The reality of the existence of this adhering layer of air

is well known to all who are familiar with electrotype manipulation.

It is also seen in the case of highly polished metals which may be

immersed in water without becoming wet. Unless this adhering layer

of air is displaced, the cement cannot adhere to the surface to

which it is applied because it cannot come in contact with it. The

most efficient agent in displacing this air is heat. Metals warmed

to a point a little above 203° F. become instantly and completely

wet when immersed in water. Hence, for cements that are used in a

fused condition, heat is the most efficient means of bringing them in

contact with the surfaces to which they are to be applied. Another

very important point is to use as little cement as possible. When the

surfaces are separated by a large mass of cement we have to depend

upon the strength of the cement itself and not upon its adhesion to

the surfaces which it is used to join; and, in general, cements are

comparatively brittle.

The cement forced out of the joint by pressing the surfaces together

should be removed while the cement is in a fused state or liquid.

This can generally be effected by wiping the surplus off, while after

solidification a certain amount of force has to be used which may

frequently break the joint.

Oil cements, which generally solidify slowly, have the advantage of

being water-proof. In cementing with oil cements, coat the surfaces to

be joined with linseed oil, or, still better, boiled linseed oil, but

in working with resinous cements apply oil of turpentine, spirit of

wine, or a fluid which will readily dissolve the cementing constituent

of the cement.

For cleansing the surfaces from grease and dirt place the articles in

strong lye and rinse off in clean water without touching the surfaces

with the hands. For painted porcelain articles which cannot be placed

in lye, it is recommended to brush the surfaces several times with

carbon disulphide.

PASTES AND MUCILAGES.

_Preparation of paste._ Ordinary paste is prepared either from flour or

starch, and according to the raw material used in its preparation, may,

therefore, be divided into starch and flour paste.

Starch is an indispensable constituent of certain parts of plants, and

plays an important part in the nutrition of the plant. It is chiefly

manufactured from potatoes, Indian corn and grain. Examined under the

microscope, it is seen to be composed of small granules consisting of

layers placed one above the other.

_Starch paste._ In stirring starch with water to a thin paste and

gradually heating it, it will be observed that at a temperature between

140° and 158° F. a peculiar change takes place; the thin milk-white

liquid becomes transparent, opalizes, and at the same time becomes

thickly fluid, in short, the starch is converted into paste. During

this process the separate layers of the starch granules become detached

somewhat in the same manner as an opening bud, whereby they absorb

water, and the peculiar mass, called paste, is formed. That paste is

not a solution is easily proved by the fact that on attempting to

filter starch-paste only water drains off, while the starch remains

upon the filter and gradually dries to a horny mass.

Paste left to itself soon decomposes, especially during the hot season

of the year; it becomes sour through the formation of lactic acid,

butyric acid, acetic acid, and other substances, and loses its adhesive

power.

In preparing paste, the following rules must be especially observed:

Divide the starch in water by constant stirring so as to form a

homogeneous, rather thinly liquid fluid, and then add boiling water

in small portions, stirring constantly. The conversion of the starch

into paste is recognized by the thickening of the entire mass and

the appearance of opalescence, when it is only necessary to add the

required quantity of water to give the paste the desired consistency.

If white lumps are observed, it is an indication that the starch has

not been thoroughly mixed with the water, and that certain portions of

it have remained dry. Paste containing such lumps cannot be applied

with any degree of uniformity, and besides it possesses less adhesive

power. Nothing can be done to remedy the evil except diluting the

paste with a considerable quantity of water and boiling, with constant

stirring, until the mass is perfectly homogenous.

Starch paste prepared in a proper manner possesses great adhesive

power, and, when applied in a thin layer, dries to an almost colorless

coating. Pure starch paste is used for many purposes. It serves not

only for pasting paper, wall paper, etc., but also for sizing tissues,

such as paper-muslin, linen, etc., in order to give them lustre, body,

and, under certain circumstances, greater weight. To increase the

weight of linen, white lead or heavy spar is frequently mixed with the

starch.

_Flour paste._ The principal constituent of flour, besides starch, is

gluten. It is obtained in a pure state by tying flour in a linen bag

and kneading it under water so long as the latter is rendered turbid by

particles of starch. The gluten remaining in the bag is a light-brown,

very tenacious mass, drawing threads between the fingers, and, as

regards its chemical properties, is closely allied to albumen and

caseine. Gluten, like the last-mentioned substances, shows a tendency

to form combinations with lime which gradually solidify, and it can

therefore be used for preparing cements. Like albumen and caseine,

it speedily putrefies if exposed to the air in a moist state, and in

decomposing forms products which have a very unpleasant odor.

Flour paste is prepared in precisely the same manner as starch paste,

but while the latter is white, flour paste, even if prepared from the

best wheat flour, has always a yellow-brown color. As regards adhesive

power it is superior to starch paste, but is less durable.

There are many means to prevent the spoiling of paste. With paste

once dry and kept so, there is no danger of spoiling, but if it

is alternately exposed to dampness and dryness, as for instance

with wall-paper hung on walls not entirely dry, decomposition will

unavoidably take place, and the wall paper will become spotted and fall

off the wall.

Provided either starch or flour paste is protected against drying in,

it can be kept unchanged for a long time by the addition of a small

quantity of carbolic acid.

For hanging wall-paper an addition of alum is, generally speaking, more

suitable than carbolic acid.

In hanging wall-paper the wall is generally first sized with

glue water. By the alum coming in contact with glue an insoluble

leather-like combination is formed, which not only resists

decomposition, but by far surpasses ordinary paste as regards adhesive

power, so that when the paper is to be removed from the wall it has

to be scraped and torn off in small pieces, while that hung without

previous sizing of the wall is readily removed in large pieces.

But alum cannot be used for preserving a glue solution, as it would

cause it to coagulate to a flaky mass. Carbolic acid is, on the

other hand, an excellent means for the purpose, but to prevent its

characteristic empyreumatic odor from making itself too sensibly

felt, no more than about one two-thousandth of the weight of the glue

solution should be added.

_Shoemakers’ paste._ In addition to being cheap, no other paste adheres

as well to leather as the so-called shoemakers’ paste. With it leather

can be secured not only to leather, but also to woven materials, paper,

etc. Though its preparation is very simple, it is connected with some

disagreeable features consisting chiefly in the development of a truly

terrible stench.

The paste is prepared by stirring crushed barley with hot water to

a thick paste and adding small portions of hot water, so that the

temperature of the mass is kept at between 86° to 104° F. In a few

days the mass commences to develop gas, which shows at first no odor,

but soon the development of gas becomes stronger and an acid odor is

perceptible, which in a short time is replaced by a terrific stench

which, as before mentioned, affects the olfactory organs in a most

unpleasant manner.

In consequence of the acid and putrid fermentation the pasty mass

gradually loses its granular condition, and is finally converted into a

homogeneous, thickly fluid mass of a brown color, which draws threads

between the fingers, and possesses great adhesive power. When this is

the case, decomposition, which otherwise would go on until nothing

remained but a watery and acid fluid, is interrupted by lowering the

temperature of the paste by ladling it from the vat or by adding a

small quantity of carbolic acid.

To render the stench developed during the fermentation of the paste

innoxious, the vat in which it is prepared should be provided with

a well-fitting cover, in which is fitted a stovepipe passing into a

chimney connected with a kitchen range or furnace, in which a fire is

frequently burnt.

By kneading shoemaker’s paste together with indifferent substances it

can be used as a cement for various purposes. The substances best

adapted for the purpose are burnt lime slaked to a powder, whiting,

zinc white, pipe clay, ochre, etc.

_Gum arabic._ This gum is an exudation from certain tropical species of

acacia, and consists essentially of arabine, which has the composition

C_{12}H_{11}O_{11}. The best gum arabic is that in the form of very

pale-yellow, brittle pieces; golden-yellow to brownish pieces are not

valued as highly, though they give a solution of considerable adhesive

power.

Gum arabic dissolves in water, but not in alcohol, and therefore can

not be employed for cements in the preparation of which solutions of

resins in spirit of wine are to be used.

There are other products of vegetable life, which are also in commerce,

called gums, but dissolve partly in spirit of wine. To this class

belongs the gum ammoniac mentioned in some receipts for cements. As it

is rather expensive, it is seldom used by itself as a cement.

_Dextrine_ is extensively used in place of gum arabic in printing

wall-papers, for stiffening and glazing cards and paper, for thickening

the colors of calico printers, in making mucilages, etc. It is prepared

by heating starch previously moistened with nitric acid in an oven,

and can also be produced by heating paste with malt extract or very

dilute sulphuric acid. There is a current anecdote which attributes the

discovery of dextrine to a conflagration at a starch factory where one

of the workmen who assisted in quenching the fire observed the gummy

properties of the water which had been thrown over the torrefied starch.

Commercial dextrine forms pale-yellow to dark-brown masses. These

masses dissolve readily in water, and form solutions which, as regards

adhesive power, compare favorably with those prepared from gum arabic.

The mucilage is prepared by simply stirring the pulverized dextrine

with water to a thickly-fluid liquid.

To preserve mucilage unchanged for any length of time, and to

prevent the disagreeable formation of mould upon its surface, it is

recommended to dissolve some salicylic acid in the water to be used for

preparing the mucilage.

Dextrine is usually prepared on a large scale by moistening 10 parts of

starch with 3 parts of water acidulated with 1/100 part of nitric acid.

The mixture is allowed to dry, and is then spread upon trays in layers

about three-quarters of an inch deep in an oven, where it is heated for

about one hour to 239° F. Sometimes large drums revolving over a fire

are used, or, in order to keep up a uniform temperature, the starch is

placed in a copper cylinder suspended in a vessel with oil which is

heated to 356° F. The object of the addition of nitric acid is to allow

the starch to be converted into dextrine at a temperature which would

be inadequate to effect the transformation of starch alone.

Dextrine is also frequently prepared by allowing germinated barley or

malt to act upon starch. Heat 350 to 400 parts of water to about 77°

F., and after adding 5 to 10 parts of dry malt, raise the temperature

to 140° F. Then add 100 parts of starch, and after mixing the whole

thoroughly together, raise the temperature to about 158° F. for twenty

minutes. The mass, which appears at first milky and sticky, will

gradually become as liquid as water by the conversion of the starch

into gum through the action of the malt. To prevent the conversion

of the gum into sugar by the diastase of the malt, the fluid must be

quickly brought to the boiling-point, and, after cooling, filtered

and evaporated to the consistency of syrup. In cooling, the mass

gelatinizes to a jelly, which after drying is hard and brittle.

According to Blumenthal’s method, a drum which can be hermetically

closed, is filled two-thirds full with dry starch flour by means of a

funnel. A stirring apparatus is then set in motion, and the acid which

is contained in a graduated cylinder is sprayed into the drum by means

of a special contrivance.

In a drum 5 feet long and 3¼ feet in diameter, 220 lbs. of potato

starch can be uniformly mixed in 5 minutes with about 9 ozs. of nitric

acid of 40° B., and the drum emptied by opening the slide. Starch thus

treated may be brought into the oven without previous drying.

Heuzé gives the following method: Four and a half pounds of nitric

acid of 1.4 specific gravity together with 300 quarts of water are

mixed with 2,200 lbs. of starch, and boiled to form a mass which,

when exposed to the air becomes dry. It is sometimes effected at 177°

F., but it becomes a paste at 212° to 230° F. The starch changes into

dextrine in an hour or an hour and a half at the most; it is white and

soluble in water.

_Tragacanth, or gum tragacanth_, exudes from _Astragalus verus_, a

tree indigenous to Asia. The term gum is a misnomer, as tragacanth

does not actually dissolve in water nor in spirit of wine, but merely

swells up in water to a soft gelatinous mass. Tragacanth consists of

irregular pieces of a pure white to yellowish color. It is chiefly used

for confectioner’s purposes, though sometimes as a paste for fancy

articles. This variety of gum is found, together with arabine, in the

gum which exudes from cherry, plum, almond, and apricot trees, and

gives the mucilaginous character to the watery decoctions prepared from

certain seeds, such as linseed and quince-seed, and from the root of

marshmallow.

PASTES AND MUCILAGES FOR SPECIAL PURPOSES.

_Starch paste._ Corn starch 8 ozs., cold water ½ pint, boiling water 1

gallon.

Beat up the starch in the cold water until reduced to a creamy

consistence, then pour the mixture into the boiling water and stir

briskly until the white, semi-opaque mass, becomes transparent. Should

it fail to do so, place it over the fire, and boil until the desired

result is obtained, stirring constantly.

_Flour paste._ Wheat flour 4 lbs., cold water 2 quarts, alum 2 ozs.,

hot water ½ pint, boiling water 2 gallons.

Glue, gelatine, animal charcoal, phosphorous, cements, pastes and mucilages · 第 11 / 12 章