a solution of pectic acid of 40° to 45° Bé., and with a certain
percentage of an alkaline carbonate—for instance, potassium carbonate
of commerce—in the proportion of 1 part of carbonate to about 4 parts
of the solution. The wood remains immersed in this composition for
12 hours; then it is taken out and drained from 8 to 15 hours, the
time varying according to the nature of the wood and the temperature.
In consequence of this second bath, the betulin which was introduced
through the first immersion, is fixed in the interior of the mass. If
it is desirable to make the wood more durable and to give it special
qualities of density, hardness, and elasticity, it must be submitted
to strong pressure. In thus supplementing the chemical with mechanical
treatment, the best results are obtained.
X.—A receiver of any form or dimensions is filled with a fluid
whose boiling point is above 212° F., such as heavy tar oil, saline
solutions, etc. This is kept at an intermediate temperature varying
between 212° F. and the boiling point; the latter will not be reached,
but if into this liquid a piece of wood is plunged, an agitation
analogous to boiling is manifested, produced by the water and sap
contained in the pores of the wood. These, under the action of a
temperature above 212° F., are dissolved into vapor and traverse the
bath.
If the wood is left immersed and a constant temperature maintained
until every trace of agitation has disappeared, the water in the
pores of the wood will be expelled, with the exception of a slight
quantity, which, being in the form of vapor, represents only the
seventeen-hundredth part of the original weight of the water contained;
the air which was present in the pores having been likewise expelled.
If the liquid is left to cool, this vapor is condensed, forming a
vacuum, which is immediately filled under the action of the atmospheric
pressure. In this way the wood is completely saturated by the contents
of the bath, whatever may be its form, proportions or condensation.
To attain the desired effect it is not necessary to employ heavy oils.
The latter have, however, the advantage of leaving on the surface of
the prepared pieces a kind of varnish, which contributes to protect
them against mold, worms, moisture, and dry rot. The same phenomenon
of penetration is produced when, without letting the wood grow cold in
the bath, it is taken out and plunged immediately into a cold bath of
the same or of a different fluid. This point is important, because it
is possible to employ as fluids to be absorbed matters having a boiling
point below 212° F., and differing in this respect from the first bath,
which must be composed of a liquid having a boiling point above 212° F.
If, instead of a cold bath of a homogeneous nature, two liquids of
different density separated in two layers, are employed, the wood can,
with necessary precautions, be immersed successively in them, so
that it can be penetrated with given quantities of each. Such liquids
are heavy tar oil and a solution of zinc chloride of 2° to 4° Bé. The
first, which is denser, remains at the bottom of the vessel, and the
second above. If the wood is first immersed in a saline solution, it
penetrates deep into the pores, and when finally the heavy oil is
absorbed, the latter forms a superficial layer, which prevents the
washing out of the saline solution in the interior, as well as the
penetration of moisture from the outside. {779}
XI.—Numerous experiments have been made with all kinds of wood, even
with hard oak. In the preparation of oak railway ties it was discovered
that pieces subjected to a temperature of 212° F. in a bath of heavy
tar oil for 4 hours lost from 6 to 7 per cent of their weight,
represented by water and albuminous substances, and that they absorbed
in heavy oil and zinc chloride enough to represent an increase of from
2 to 3 per cent on their natural original weight. The oak wood in
question had been cut for more than a year and was of a density of 1.04
to 1.07.
This system offers the advantage of allowing the absorption of
antiseptic liquids without any deformation of the constituent elements
of the wood, the more as the operation is performed altogether in open
vessels. Another advantage is the greater resistance of the wood to
warping and bending, and to the extraction of metallic pieces, such as
nails, cramp irons, etc.
XII.—In the Kyanizing process seasoned timber is soaked in a solution
of bichloride of mercury (corrosive sublimate) which coagulates the
albumen. The solution is very poisonous and corrodes iron and steel,
hence is unsuited for structural purposes in which metallic fastenings
are used. The process is effective, but dangerous to the health of the
workers employed.
XIII.—The Wellhouse process also uses zinc chloride, but adds a
small percentage of glue. After the timber has been treated under
pressure the zinc chloride solution is drawn off and one of tannin is
substituted. The tannin combines with the glue and forms an insoluble
substance that effectually seals the pores.
XIV.—The Allardyce process makes use of zinc chloride and dead oil of
tar, the latter being applied last, and the manner of application being
essentially the same for both as explained in the other processes.
XV.—The timber is boiled in a solution of copper, iron, and aluminum
sulphate, to which a small quantity of kainit is added.
XVI.—In the creo-rosinate process the timber is first subjected to a
steaming process at 200° F. to evaporate the moisture in the cells;
the temperature is then gradually increased to 320° F. and a pressure
of 80 pounds per square inch. The pressure is slowly reduced to 26
inches vacuum, and then a solution of dead oil of tar, melted rosin,
and formaldehyde is injected. After this process the timber is placed
in another cylinder where a solution of milk of lime is applied at a
temperature of 150° F. and a pressure of 200 pounds per square inch.
XVII.—The vulcanizing process of treating timber consists essentially
in subjecting it to a baking process in hot air which is heated to a
temperature of about 500° F. by passing over steam coils. The heat
coagulates the albumen, expels the water from the cells, kills the
organisms therein, and seals the cells by transforming the sap into a
preservative compound. This method is used with success by the elevated
railway systems of several cities.
XVIII.—A durable coating for wood is obtained by extracting petroleum
asphalt, with light petroleum, benzine, or gasoline. For this purpose
the asphalt, coarsely powdered, is digested for 1 to 2 days with
benzine in well-closed vessels, at a moderately warm spot. Petroleum
asphalt results when the distillation of petroleum continued until a
glossy, firm, pulverizable mass of conchoidal fracture and resembling
colophony in consistency remains. The benzine dissolves from this
asphalt only a yellowish-brown dyestuff, which deeply enters the wood
and protects it from the action of the weather, worms, dry rot, etc.
The paint is not opaque, hence the wood retains its natural fiber. It
is very pleasant to look at, because the wood treated with it keeps
its natural appearance. The wood can be washed off with soap, and is
especially suited for country and summer houses.
XIX.—A liquid to preserve wood from mold and dry rot which destroys the
albuminous matter of the wood and the organisms which feed on it, so
there are neither germs nor food for them if there were any, is sold
under the name of carbolineum. The specific gravity of a carbolineum
should exceed 1.105, and should give the wood a fine brown color. It
should, too, be perfectly waterproof. The three following recipes can
be absolutely relied on: _a._ Heat together and mix thoroughly 95
pounds of coal-tar oil and 5 pounds of asphalt from coal tar. _b._
Amalgamate together 30 pounds of heavy coal-tar oil, 60 pounds of crude
wood-tar oil, and 25 pounds of heavy rosin oil. _c._ Mix thoroughly 3
pounds of asphalt, 25 pounds of heavy coal-tar oil, and 40 pounds of
heavy rosin oil.
XX.—Often the wooden portions of machines are so damaged by dampness
prevailing in the shops that the {780} following compound will be found
useful for their protection: Melt 375 parts of colophony in an iron
vessel, and add 10,000 parts of tar, and 500 parts of sulphur. Color
with brown ocher or any other coloring matter diluted with linseed oil.
Make a first light application of this mixture while warm, and after
drying apply a second coat.
XXI.—For enameling vats, etc., 1,000 parts of brown shellac and 125
parts of colophony are melted in a spacious kettle. After the mass has
cooled somewhat, but is still thinly liquid, 6.1 parts of alcohol (90
per cent) is gradually added. In order to prevent the ignition of the
spirit vapor, the admixture of spirit is made at a distance from the
stove. By this addition the shellac swells up into a semi-liquid mass,
and a larger amount of enamel is obtained than by dissolving it cold.
The enamel may be used for wood or iron.
The wood must be well dried; only then will the enamel penetrate into
the pores. Two or three coats suffice to close up the pores of the wood
thoroughly and to render the surface smooth and glossy. Each coating
will harden perfectly in several hours. The covering endures a heat
of 140° to 150° F. without injury. This glaze can also be mixed with
earth colors. Drying quickly and being tasteless, its applications
are manifold. Mixed with ocher, for instance, it gives an elegant and
durable floor varnish, which may safely be washed off with weak soda
solution. If it is not essential that the objects be provided with
a smooth and glossy coating, only a preservation being aimed at the
following coat is recommended by the same source: Thin, soluble glass
(water glass) as it is found in commerce, with about 24 per cent of
water, and paint the dry vessel rather hot with this solution. When
this has been absorbed, repeat the application, allow to dry, and coat
with a solution of about 1 part of sodium bicarbonate in 8 parts of
water. In this coating silicic acid is separated by the carbonic acid
of the bicarbonate; from the water glass (sodium silicate) absorbed
by the pores of the wood, which, as it were, silicifies the wooden
surfaces, rendering them resistive against the penetration of liquids.
The advantages claimed for both processes are increased durability and
facilitated cleaning.
XXII.—Tar paints, called also mineral or metallic paints, are sold in
barrels or boxes, at varying prices. Some dealers color them—yellow
ocher, red ocher, brown, gray, etc. They are prepared by mixing equal
parts of coal tar and oil of turpentine or mineral essence (gasoline).
The product, if it is not colored artificially, is of a brilliant
black, even when cold. It dries in a few hours, especially when
prepared with oil of turpentine. The paints with mineral essence are,
however, generally preferred, on account of their lower cost. Either
should be spread on with a hard brush, in coats as thin as possible.
They penetrate soft woods, and even semi-hard woods sufficiently deep,
and preserve them completely. They adhere perfectly to metals. Their
employment can, therefore, be confidently advised, so far as concerns
the preservation directly of iron cables, reservoirs, the interior
surface of generators, etc. However, it has been shown that atmospheric
influence or variations of temperature cause the formation of
ammoniacal solutions, which corrode the metals. Several companies for
the care and insurance of steam engines have for some time recommended
the abandonment of tar products for applications of this kind and the
substitution of hot linseed oil.
XXIII.—Coal-tar paints are prepared according to various formulas. One
in current use has coal tar for a base, with the addition of gum rosin.
It is very black. Two thin coats give a fine brilliancy. It is employed
on metals, iron, sheet iron, etc., as well as on wood. It dries much
quicker than the tars used separately. Its preserving influence against
rust is very strong.
The following Tissandier formula has afforded excellent results. Its
facility of preparation and its low cost are among its advantages. Mix
10 parts of coal tar, 1 to 1.6 parts of slaked lime, 4,000 parts of oil
of turpentine, and 400 parts of strong vinegar, in which 1/5 part
of cupric sulphate has been previously boiled. The addition of 2 or 3
cloves of garlic in the solution of cupric sulphate aids in producing
a varnish, brilliant as well as permanent. The compound can be colored
like ordinary paints.
XXIV.—Rectified rosinous oil for painting must not be confounded with
oils used in the preparation of lubricants for metallic surfaces
exposed to friction. It contains a certain quantity of rosin in
solution, which, on drying, fills the pores of the wood completely, and
prevents decomposition from the action of various saprophytic fungi.
It is well adapted to the preservation of pieces to be buried in the
ground or exposed to the inclemency {781} of the weather. Paints can
also be prepared with it by the addition of coloring powders, yellow,
brown, red, green, blue, etc., in the proportion of 1 kilo to 5 liters
of oil. The addition ought to take place slowly, while shaking, in
order to obtain quite a homogeneous mixture. Paints of this kind are
economical, in consequence of the low price of rosin, but they cannot
be used in the interior of dwellings by reason of the strong and
disagreeable odor disengaged, even a long time after their application.
As an offset, they can be used like tar and carbonyl, for stalls,
stables, etc.
«To Prevent Warping.»—Immerse the wood to be worked upon in a
concentrated solution of sea salt for a week or so. The wood thus
prepared, after having been worked upon, will resist all changes of
temperature.
«STAINS FOR WOOD.»
In the staining of wood it is not enough to know merely how to prepare
and how to apply the various staining solutions; a rational exercise of
the art of wood staining demands rather a certain acquaintance with the
varieties of wood to be operated upon, a knowledge of their separate
relations to the individual stains themselves; for with one and the
same stain very different effects are obtained when applied to the
varying species of wood.
Such a diversity of effects arises from the varying chemical
composition of wood. No unimportant rôle is played by the presence in
greater or lesser quantities of tannin, which acts chemically upon
many of the stains and forms with them various colored varnishes in
the fibers. Two examples will suffice to make this clear. (1) Let us
take pine or fir, in which but little of the tanning principle is
found, and stain it with a solution of 50 parts of potassium chromate
in 1,000 parts of pure water; the result will be a plain pale yellow
color, corresponding with the potassium chromate, which is not fast
and as a consequence is of no value. If, with the same solution, on
the contrary, we stain oak, in which the tanning principle is very
abundant, we obtain a beautiful yellowish-brown color which is capable
of withstanding the effects of both light and air for some time; for
the tannin of the oak combines with the penetrating potassium chromate
to form a brown dyestuff which deposits in the woody cells. A similar
procedure occurs in the staining of mahogany and walnut with the
chromate because these varieties of wood are very rich in tannin.
(2) Take some of the same pine or fir and stain it with a solution of
20 parts of sulphate of iron in 1,000 parts of water and there will be
no perceptible color. Apply this stain, however, to the oak and we get
a beautiful light gray, and if the stain be painted with a brush on the
smoother oaken board, in a short time a strong bluish-gray tint will
appear. This effect of the stain is the result of the combination of
the green vitriol with the tannin; the more tannin present, the darker
the stain becomes. The hardness or density of the wood, too, exerts
a marked influence upon the resulting stain. In a soft wood, having
large pores, the stain not only sinks further in, but much more of
it is required than in a hard dense wood; hence in the first place a
stronger, greasier stain will be obtained with the same solution than
in the latter.
From this we learn that in soft woods it is more advisable to use a
thinner stain to arrive at a certain tone; while the solution may be
made thicker or stronger for hard woods.
The same formula or the same staining solution cannot be relied upon
to give the same results at all times even when applied to the same
kinds of wood. A greater or lesser amount of rosin or sap in the wood
at the time the tree is felled, will offer more or less resistance to
the permeating tendencies of the stain, so that the color may be at one
time much lighter, at another darker. Much after the same manner we
find that the amount of the tanning principle is not always equal in
the same species of wood.
Here much depends upon the age of the tree as well as upon the
climatic conditions surrounding the place where it grew. Moreover,
the fundamental color of the wood itself may vary greatly in examples
of the same species and thus, particularly in light, delicate shades,
cause an important delay in the realization of the final color tone.
Because of this diversification, not only in the different species
of wood, but even in separate specimens of the same species, it is
almost impossible always, and at the first attempt, to match a certain
predetermined color.
It is desirable that trials at staining should first be made upon
pieces of board from the same wood as the object to be stained; the
results of such experiments furnishing exact data concerning the
strength and composition of the stain to be employed for the exact
reproduction of a prescribed color. {782} Many cases occur in which the
color tone obtained by staining cannot always be judged directly after
applying the stain. Especially is this the case when stain is employed
which slowly develops under the action of the air or when the dyestuff
penetrates only slowly into the pores of the wood. In such cases the
effect of the staining may only be fully and completely appreciated
after the lapse of 24 or 48 hours.
Wood that has been stained should always be allowed 24 or 48 hours to
dry in ordinary temperatures, before a coat of varnish, polish, or wax
is applied. If any dampness be left in the wood this will make itself
apparent upon the varnish or polish. It will become dull, lose its
glossy appearance, and exhibit white spots which can only be removed
with difficulty. If a certain effect demand the application of two or
more stains one upon the other, this may only be done by affording each
distinct coat time to dry, which requires at least 24 hours.
Not all the dyes, which are applicable to wood staining, can be
profitably used together, either when separately applied or mixed. This
injunction is to be carefully noted in the application of coal tar or
aniline colors.
Among the aniline dyes suitable for staining woods are two groups—the
so-called acid dyes and the basic dyes. If a solution of an acid dye be
mixed with a basic dye the effect of their antagonistic dispositions is
shown in the clouding up of the stain, a fine precipitate is visible
and often a rosin-like separation is noticeable.
It is needless to say that such a staining solution is useless for
any practical purpose. It cannot penetrate the wood fibers and would
present but an unseemly and for the most part a flaky appearance.
In preparing the stains it is therefore of the greatest importance
that they remain lastingly clear. It would be considerably of
advantage, before mixing aniline solutions of which the acid or basic
characteristics are unknown, to make a test on a small scale in a
champagne glass and after standing a short time carefully examine the
solution. If it has become cloudy or wanting in transparency it is a
sign that a separation of the coloring matter has taken place.
The mixing of acid or basic dyestuffs even in dry powdered form is
attended with the same disadvantages as in the state of solubility, for
just as soon as they are dissolved in water the reactions commence and
the natural process of precipitation takes place with all its attending
disagreeable consequences.
«COLOR STAINS:»
«Bronze.»—I.—Prepare first a thin glue size by soaking good animal glue
over night in cold water and melting it next morning in the usual water
bath. Strain it, before using, through old linen or cheese cloth into a
clean vessel. Sandpaper smooth and dust the articles, then apply with a
soft bristle brush 2 or 3 coats of the size, allowing sufficient time
for each coat to harden before applying the next. Now, a ground coat
made by thoroughly mixing finely bolted gilders’ whiting and glue size
is applied, and when this has become hard it is rubbed to a smooth,
even surface with selected fine pumice, and then given 1 coat of thin
copal varnish. When this is nearly but not quite dry, the bronze powder
is applied with a suitable brush or wad of cotton, and when dry the
surplus bronze is removed with the same tool. If collected on clean
paper, the dusted-off bronze powder may be used again.
II.—Diluted water-glass solution makes a good ground for bronze. Bronze
powder is sprinkled on from a wide-necked glass tied up with gauze, and
the excess removed by gently knocking. The bronze powder adheres so
firmly after drying that a polish may be put on by means of an agate.
The process is especially useful for repairing worn-off picture frames,
book ornamentations, etc. The following bronze ground also yields good
results: Boil 11,000 parts of linseed oil with 25 parts of impure zinc
carbonate, 100 parts of red lead, 25 parts of litharge, and 0.3 parts
of mercuric chloride, until a drop taken out will stand like a pea upon
a glass surface. Before complete cooling, the mass is diluted with oil
of turpentine to a thick syrup.
«Ebony Stains.»—I.—To 1 pint of boiling water add 3/4 ounce of
copperas and 1 ounce logwood chips. Apply this to the wood hot. When
the surface has dried thoroughly wet it with a solution composed of 7
ounces steel filings dissolved in 1/4 pint of vinegar.
II.—Give the wood several applications of a stout decoction of logwood
chips, finishing off with a free smear of vinegar in which rusty nails
have been for some time submerged.
III.—In 1 quart of water boil 1/4 pound of logwood chips,
subsequently adding 1/2 ounce pearl ash, applying the mixture {783}
hot. Then again boil the same quantity of logwood in the same quantity
of water, adding 1/4 ounce of verdigris and 1/4 ounce of copperas,
after which strain and put in 1/4 pound of rusty steel filings.
With this latter mixture coat the work, and, should the wood not be
sufficiently black, repeat the application.
«Metallic Luster.»—A valuable process to impart the luster of metal to
ordinary wood, without injuring its natural qualities, is as follows:
The wood is laid, according to its weight, for 3 or 4 days in a caustic
alkaline solution, such as, for instance, of calcined soda, at a
temperature of 170° F. Then it is at once placed in a bath of calcium
hydrosulphite, to which, after 24 to 36 hours, a saturated solution
of sulphur in caustic potash is added. In this mixture the wood is
left for 48 hours at 100° to 120° F. The wood thus prepared, after
having been dried at a moderate temperature, is polished by means of
a smoothing iron, and the surface assumes a very handsome metallic
luster. The effect of this metallic gloss is still more pleasing
if the wood is rubbed with a piece of lead, zinc, or tin. If it is
subsequently polished with a burnisher of glass or porcelain, the wood
gains the brilliancy of a metallic mirror.
«Nutwood.»—One part permanganate of potassium is dissolved in 30 parts
clear water; with this the wood to be stained is coated twice. After an
action of 5 minutes, rinse off with water, dry, oil, and polish. It is
best to prepare a fresh solution each time.