DYEING. 
will, in the course of a few hours, be fit for 
use. 
The solution of indigo in sulphuric acid, 
has been hitherto only used for dyeing 
wool and silk. The affinity of vegetable 
substances for indigo is not sufficiently 
strong to separate it from the sulphuric 
acid. It cannot therefore be employed to 
advantage in dyeing cotton or linen. 
Attempts have been made to dye cloth 
with Prussian blue, but no method ha* yet 
been found to make this colour apply Itself 
evenly, sufficiently certain and perfect for 
general use. This process deserves farther 
experiments, as the colour produced by it 
was very beautiful, and not liable to change, 
though exposed to all the vicissitudes of the 
air. But dust and rubbing injure it ; and any 
touch of an alkaline liquor destroys it alto- 
gether. The process in which stuffs, pre- 
viously impregnated with alum and cop- 
peras, are submitted to a solution of Prus- 
sian alkali, seems that most likely to succeed 
in diffiising the dye equally if improved by 
farther trials. Perhaps also a solution of 
caustic alkali might form a sufficient solvent 
for the Prussian blue, if ground with it, to 
admit of its being used in somewhat the 
same way as indigo. 
Of dyeing W ool red. 
Red colours are of various shades ac- 
cording to the nature of the colouring mat- 
ters used. They all require mordants to 
render them permanent. The principle 
shades of red, are scarlet, crimson, and 
madder red. 
Madder red is only employed for dyeing 
coarse woollen stuffs. To produce this red, 
the stuffs are first boiled for two or three 
hours with alum and tartar ; they are then 
left to drain, slightly wrung out, and then 
put into a linen bag, and carried to a cool 
place, where they are to remain a few 
days. Some recommend five ounces of 
alum and one of tartar to each pound of 
wool ; by encreasing the proportion of tar- 
tar, a deep and permanent cinnamon colour 
is produced instead of red ; others advise to 
use only a seventh part of tartar. The 
madder bath should not exceed the tempe- 
rature which the hand can bear ; if let to 
boil, the colour will be different from that 
required. When the water is at this heat, 
Hellot recommends half a pound of grape 
madder to be put into it for every pound of 
wool to be dyed. It is to be well stirred 
before the wool is introduced, which should 
remain in it for an hour without boiling, ex- 
cept for a few minutes towards the end of 
this period, to make the combination of the 
colouring matter with the stuff more cer- 
tain. 
Madder reds are sometimes rosed, as it is 
called, with archil and brazil wood. In 
this way they become more beautiful and 
velvety, but the brightness thus given is not 
permanent. 
When sulphate of copper is employed as 
a mordant, the madder dye yields a clear 
brown, somewhat inclined to a yellow ; 
when solution of tin is used, the tint, ac- 
cording to Berthollet, is somewhat brighter 
than that obtained by the common method, 
but is always more inclined to yellow or 
fawn colour. 
The red procured from kermes is finer 
than that from madder. The kermes is an 
insect found on a small species of live oak in 
Languedoc, Spain, Portugal, and other 
places ; the females alone are used, tliey are 
of the shape and size of a pea, and of a red- 
dish brown colour. 
To dye woollen yarn with kermes, it is 
first boiled half an hour in water with 
bran ; then two hours in a fresh bath, of one 
fifth of Roman alum, and one tenth of tartar 
dissolved in sour water ; after this, it is left 
in a linen bag for some days in a cool 
place. To obtain a full colour, as much 
kermes as equals three fourths, or even the 
whole of the weight of the yarn is put into 
a warm bath, and the wool is put in at the 
first boiling. As cloth is less dense than 
wool, either spun or in the fleece, it re- 
quires one fourth less of the salts in boiling, 
and of the kermes in the bath. 
The scarlet made by kermes was called 
scarlet in grain from the insect resembling a 
grain ; it ba^uch less bloom than that pro- 
cured from cochineal ; but is more perma- 
nent, and spots of grease may be discharged 
from it without injury. Since the art of 
heightening the colour of cochineal by so- 
lution of tin has been discovered, kermes 
has not been much used. 
The scarlet produced by the preparation 
of cochineal just mentioned, is esteemed the 
finest and most splendid of any. Cloth to 
be dyed with it, is first submitted to the fol- 
lowing bath : six pounds of tartar are in- 
fused in the water made warm, for every 
hundred pounds of the cloth ; the bath is 
then stirred briskly, and when the heat has 
encreased a little more, half a pound of 
powdered cochineal is to be added, and the 
whole is then to be well mixed ; imme- 
diately afterwards, five pounds of a very 
