10. An ammoniacal solution of cochineal is used for making many violet
and mallow colours. It is prepared by infusing cochineal in water of
ammonia for 24 hours; then diluting with water, heating to ebullition,
and straining.
11. _Fine violet_ is given by ammoniacal cochineal, with alum and oxalic
acid; to which a little aceto-sulphate of indigo is added, and gum for
thickening. The following blue may be used instead of the solution of
indigo. The _mallow_ tint is given by adding a little perchloride of tin
to the above formula, and leaving out the blue.
12. _Dark blue._--Soluble Prussian blue; tartaric acid; alum; thicken
with gum.
13. _Emerald green._--One quart of decoction, equivalent to 1 pound of
Persian berries; 1 quart of infusion of quercitron, of spec. grav.
1·027; in which dissolve 12 ounces of alum in powder; and add 6 ounces
of the following blue bath for greens; thicken with 20 ounces of gum.
14. Blue bath for greens. Half a gallon of water at 140° F., 1 pound of
soluble Prussian blue, 3 ounces of tartaric acid, and 2 ounces of alum.
I. _Printing of Silks._--1. _Of the madder style._ This is one of the
most difficult to execute, requiring both much skill and experience. The
first step is the removal of the gum. A copper being nearly filled with
water, the pieces, tied up in a linen bag, are put into it, with a
quarter of a pound of soap for every pound of silk, and are boiled for 3
hours. If the silk be Indian, half an ounce of soda crystals must be
added. When the goods are taken out, they are rinsed in the river, then
passed through water at 140° F., holding 8 ounces of crystallised soda
in solution, as a scourer. They are next rinsed in cold water, and
steeped in water very faintly acidulated with sulphuric acid, during 4
hours, then rinsed, and dried.
_Preparation of Mordants._--1 gallon of boiling water; 2 pounds of alum;
dissolve:
1 pound of acetate of lead; 4 ounces of sal-ammoniac; 1 of chalk; mix
well together; after decomposition and subsidence, draw off clear.
1. _Red._--1 gallon of the above mordant, thickened with 14 ounces of
starch, and tinged with decoction of Brazil wood. If dark red be wanted,
dissolve, in a gallon of the above red, 4 ounces of sulphate of copper.
2. _Black._--1 gallon of iron liquor, of 1·056 spec. grav.; thicken with
14 ounces of starch; and dissolve in the hot paste 2 ounces of sulphate
of copper.
3. _Violet._ Take 1 gallon of iron liquor of 1·04 spec. grav.;
2 ounces of cream of tartar; 2 ounces of nitre; 2 ounces
of copperas;
1 ounce of alum: dissolve, and mix the solution with
1 gallon of gum water, containing 6 libs. of gum.
4. _Puce._ Half a gallon of red mordant; half a gallon of iron liquor
of 1·07;
7 ounces of starch for thickening colour with logwood.
_Manipulation of the above colours._--Print-on the black, then the puce,
next the violet, and, lastly the red. Dry in the hot flue, and, 48 hours
after the impression, wash away the paste. The copper employed for
dyeing is of a square form: a boil is given with bran, at the rate of 4
libs. per piece of the _foulards_: cold water is added to lower the
temperature to 130° F. The pieces must be entered with the printed
surface undermost, and winced for half an hour, taking care to keep them
expanded and well covered with the liquor: they are then taken out and
rinsed. When grounds are to be made on the foulards, 2 ounces of sumach
must be added per piece.
_Maddering._--Suppose 48 pieces are to be grounded with madder. 12
pounds of madder must be put into the copper, 1 pound of sumach, and 6
pounds of bran; the bath must be tepid when the pieces are entered: it
must be heated to 104° F. in 20 minutes, and to the boiling point in an
hour and a half. The goods must be briskly winced all the time, and
finally turned out into cold water.
When they come out of the madder bath they are much loaded with colour.
They are cleared by a boil of half an hour in bran, then turned out into
cold water, and rinsed. A copper must be now mounted with 3 pounds of
soap, 1 ounce of solution of tin, and 2 pailsful of bran, in which the
goods are to be boiled for half an hour, then rinsed, and passed through
a very dilute sulphuric acid bath. Then rinse, and dry. By following
this process a light salmon ground is obtained.
II. _Steam colours upon silk._--The same plan of operations may be
adopted here as is described for calico-printing; the main difference
being in the method of mordanting the stuffs. After boiling in soap
water, in the proportion of 4 ounces per pound of silk, the goods are
washed in cold water, and then in hot water at 140°; they are next
rinsed, passed through weak sulphuric acid, rinsed, squeezed between
rollers, and afterwards steeped in a bath containing 8 ounces of alum
per gallon, where they remain for four hours, with occasionally wincing.
They are now rinsed, and dried. The subsequent treatment resembles that
of steam-colour printed cottons.
_Black._--Take a gallon of decoction, made with 4 libs. of logwood,
with which
14 ounces of starch are to be combined: mix in
2 ounces of powdered nut-galls: boil, and pour the colour
into a pipkin containing
2 ounces of tartaric acid; 2 ounces of oxalic, both in
powder, and
2 ounces of olive oil. Stir the colour till it is cold, and
add
8 ounces of nitrate of iron, and 4 ounces of nitrate of
copper.
The red, violet, lilac, yellow colours, &c. are the same as for steam
colours upon cotton. Topical colours are also applied without mordanting
the silk beforehand. In this case a little muriate of tin is introduced.
Thus, for
_Yellow._--Take 1 gallon of a decoction, made with 4 libs. of Persian
berries: dissolve in it 8 ounces of salt of tin (muriate),
and 4 ounces of the nitro-muriatic solution of tin. Thicken
with 2 pounds of gum.
[Illustration: 246 247]
_Printing of foulard pieces._ The tables which serve for the impression
of silk goods are so constructed as to receive them in their full
breadth. Towards the part between the colour or sieve tub and the table,
the roller is mounted upon which the piece is wound. This roller, A B,
_fig._ 246., has a groove, C, cut out parallel to its axis. Into this a
bar is pressed, which fixes the end of the piece. The head, B, of the
roller is pierced with several holes, in which an iron pin passes for
stopping its rotation at any point, as is shown at B. At the other end
of the table there is placed a comb, _fig._ 247., which is supported by
pivots A B at its ends. The teeth of the comb are on a level with the
cloth.
The piece is arranged for printing as follows:--It is unwound, and its
end is brought upon the teeth of the comb, and made to pass into them by
slight taps with a brush. It is now stretched, by turning round the
roller, and fixing it by the pin-handle. After tracing the outline, the
printing blocks are applied. Care should be taken, in the course of
printing, always to fix the teeth of the comb in the middle line between
two handkerchiefs. The operation of grounding-in is much facilitated by
this plan of extension.
The pieces are washed in running water, and must be rapidly dried. The
subsequent dressing is given by gum tragacanth: they are dried upon a
stretching frame, and then folded up for the market.
III. _Mandarining of silk stuffs and chalys._--This style of printing
depends upon the property which nitric acid possesses of giving to silk
and woollen stuffs a yellow colour.
The first step is the scouring with a soap boil, as already described.
The designs are printed-on as also above described.
[Illustration: 248]
The swimming or colour-tub is usually double, and serves for two tables;
instead of being placed, therefore, at the end of the table, it is put
between two, and, consequently, behind the printer. It is formed of a
copper chest, _fig._ 248., A B C D, in which steam may circulate,
introduced by the pipe I; the excess being allowed to escape by the tube
J, as also the water of condensation. The frame is placed in the hollow
box K K. Between two such frames there is a plate of copper, L, which
closes the box; it serves for laying the plates in order to keep them
hot. At E and H are prolongations of the box, in which are set the
vessels F G for holding the reserve paste.
_Preparation of the reserve or resist paste._--Melt in a kettle 2-1/2
libs. of rosin; 1 lib. of suet: mix well, and put it into the basins F
G. By means of steam the reserve is kept melted, as well as the false
colour upon which the sieve floats. The piece of silk being laid upon
the table, and the reserve spread upon the frame, the printer heats his
block, which should be mounted with lead, if the pattern will permit,
upon the little table L. He takes up the colour from the frame, and
transfers it instantly to the piece. He must strike the block lightly,
and then lift it, lest, by its cooling, it might stick to the silk. When
the table pattern is completed, he dusts it over with sand, and proceeds
to another portion of the silk. The piece must not be taken out of the
stretch till it is quite dry, which requires usually 6 hours. Let us
consider first the most common case, that of a white upon an orange
ground. We shall afterwards describe the other styles, which may be
obtained by this process. The piece, being printed and dry, must next be
subjected to the _mandarining_ operation.
[Illustration: 249 250]
The apparatus here employed consists of a sandstone trough A B C D,
_fig._ 249. Upon the two sides, A C, B D, of this trough are fixed two
wooden planks, pierced with a hole an inch from the bottom to receive
the roller E, under which the piece passes. In this trough the acid
mixture is put. That trough is put into a wooden or copper trough, F G H
I. Into the latter, water is put, which is heated by means of steam, or
a convenient furnace. Before and behind are placed two winces, or reels,
K L: one serves to guide the piece in entering into the trough, and the
other in its leaving it. The piece falls immediately into a stream of
cold water, or, failing that, into a large back, containing a mixture of
chalk and water. The two winces are moved by handles: the velocity is
proportioned to the action of the acid. The wince L ought to be higher
than K, to allow the acid to drain off. _Fig._ 250. shows a section of
the apparatus.
The temperature of the acid mixture ought to be maintained between 95°
and 100° F.; for if it be raised higher, the resist would run the risk
of melting, and the impression would become irregular and blotty.
The proportions of the acid mixture are the following:--1 gallon of
water; and 1 gallon of nitric acid, of spec. grav. 1·288, which may be
increased with the strength of the silk. It should be a little weaker
for chalys. For the strong greens it may be 2 measures of acid of 1·288
to 1 measure of water. The duration of the passage through the acid
should be 1 minute at most.
_Mixture of orange colour, and clearing away of the resist._--The goods,
on coming out of the mandarining apparatus, are rinsed in running water;
then boiled in soap water, quickened with a little soda, at the rate of
2 libs. of the former and 4 oz. of the latter for a piece of 30 yards.
They must be worked by the wince for half an hour. They are now rinsed
in cold water, then passed through hot, again rinsed, and dried. I shall
give some examples of the mode of manufacture, which is undoubtedly one
of the most curious applications of chemical ingenuity.