Encyclopaedia Britannica > Volume 8, DIA-England

342
DYEING.
Calico-
Printing.
in some cases into an aqueous solution of bleaching pow¬
der. Indeed the processes for applying chromic acid are
varied in a great many ways, to suit the different colours
which are applied along with the yellow; as in the yel¬
low discharge for bronze, and the yellow resist on blue
already described, the yellow discharge on Turkey red,
&c. &c.
Quercitron bark is also often employed to communicate
a yellow by the calico-printers. The alumina mordant
is first applied, and the cloth is cleaned in the dung
vessel in the way described when giving an account of
madder dyeing. Quercitron bark gives out its colouring
matter at a lower heat than madder; and the parts of
the cloth to which no mordant has been applied remain
tolerably white after the cloth has been washed in cold
water.
A decoction of Persian berries constitutes likewise a
common yellow dyestuff for calico-printers. The decoc¬
tion is mixed with the requisite portion of alum to act as
a mordant; but a combination between the alumina and
the yellow colouring matter takes place without the inter¬
vention of a third agent. It is effected either by exposing
the cloth to the action of steam, or by putting the piece
into water containing an alkali or its carbonate.
4. Blue.
The usual dyestuffs for giving a blue colour to calicoes
are indigo and Prussian blue.
The method of forming the indigo vat has been already
mentioned. The cloth is dipped in the clear solution.
When taken out it is yellow, and gradually becomes blue
by absorbing oxj'gen from the atmosphere. If a deep shade
is wanted, the cloth is immersed again, when it receives an
additional quantity of indigo, which must be oxidized, as
the former was, by exposure to the air. These alternate
dips and airings are repeated till the requisite shade is
attained.
What is called 'pencil blue, is a solution of indigo in
caustic potash or soda, the indigo being de-oxidized by
means of orpiment. The solution is thickened by means
of British gum, or gum-senegal, and printed upon the
cloth either by the block or cylinder. When upon the
cloth, the indigo attracts oxygen from the air, and thus
becomes blue and fixed. The gum, alkali, loose indigo,
&c. are washed away in water.
Prussian blue may be applied to cloth in various ways.
We shall mention some of the principal of these.
1. An iron mordant is first applied to the cloth, and al¬
lowed to remain untouched till the iron has had time to be
peroxidized, and in that way become fixed. The piece is
then cleaned as for dyeing, and dipt into a solution of
prussiate of potash mixed with sulphuric acid, to disengage
the acid or cyanogen which it contains.
2. Prussian blue is dissolved in muriatic acid, oxalic
acid, perchloride of tin, or nitrate of iron, and the solution
applied immediately to the cloth in the usual way.
3. Ferrocyanic acid is printed upon the cloth, and de¬
composed by means of a steam heat, hydrocyanic acid
escapes, and cyanodide of iron remains in the cloth. It
becomes blue by exposure to the air, or by being put into
. a weak solution of bleaching powder, or of bichromate of
potash.
Logwood forms a bluish compound with the salts of
copper; but this colour is exceedingly fugitive, and the
use of it has been long laid aside.
5. Black.
Various methods are employed by the calico-printers to
produce a black upon cotton. An iron mordant of the
specific gravity 1-05 gives a black with madder. The
common aluminous mordant gives a black when cloth im- Cali i.
pregnated with it is dyed in logwood. A chemical black Print |
is made from a decoction of nutgalls mixed with nitrated '>-~Y 1
peroxide of iron. Another chemical black is formed by
mixing a decoction of logwood with a solution of sulphate
of iron.
If cloth be dyed successively blue, red, and yellow, it
becomes black.
6. Buff.
To produce this colour, the cloth is printed with a mix¬
ture of sulphate and acetate of iron. After having had
time to be partly peroxidized and partially decomposed,
it is washed in water; or if a stronger buff is wanted, it is
rinsed in cream of lime till the protoxide is converted into
the red. No mordant is required, as the peroxide of iron
has a strong affinity for cotton cloth.
7. Gold.
For this colour the process is the same as for buff. The
only difference is, that the solution is stronger.
8. Orange.
The most beautiful orange is given by means of dichro¬
mate of lead. It is obtained by saturating bichromate of
potash with potash or lime, and immersing in it while hot,
cloth printed with a salt of lead. Nitric acid changes
this orange into yellow, by uniting with half the oxide of
lead.
9. Green.
The fast green, discovered by Mr James Thomson of
Primrosehill, near Clitheroe, and commonly known by the
name of Warwick's green, is a mixture of the pencil blue
already described, and aluminated potash. The mixture
is thickened and applied as the blue is. The alumina
is then precipitated from its alkaline solution by being
passed through a weak solution of sal ammoniac or sul¬
phate of magnesia. The cloth is then dyed yellow in
quercitron bark. It is sufficiently known that the two co¬
lours blue and yellow form a green.
Carbonate of copper makes a poor faint green upon cloth,
while the hydrated black oxide forms a bright blue. It is
obtained bjr printing on a strong solution of copper, and
dipping the cloth, when dry, into strong caustic potash or
soda.
The colour called Scheele's green is a mixture of arsenite
of copper and the hydrated black oxide. It is obtained
by printing on the cloth a strong solution of copper thick¬
ened with gum, and then dipping it into a mixture of ar¬
senite of potash and caustic potash. Hot water destroys
this colour, by depriving the oxide of copper of its water.
A green is obtained from Prussian blue and yellow ber¬
ries, by mixing together ferrocyanic acid, yellow berries,
and an aluminous mordant, and subjecting them to the
action of steam.
Various other greens are attained by printing yellows
over blues previously produced.
Saxon green is produced by printing a solution of ceru-
lin over a yellow formed by dyeing the aluminous mor¬
dant with quercitron bark or weld. The cerulin adheres
to those parts of the cloth which have been dyed yellow,
but very slightly to the white cloth, from which it is easi¬
ly washed away.
10. Lilac.
This colour is communicated to cloth by printing on a
much diluted mixture of the iron and aluminous mordants
thickened with gum-senegal. The cloth is then dyed in
madder exactly as described for producing a red.