DYEING. 
it will be fit for dyeing. Its heat should be 
just what the hand can bear without pain. 
The silk is prepared for this hath by being 
boiled with thirty pounds of soap for every 
hundred pounds of silk, and being after- 
wards well cleansed from it by two or more 
beetlings in a stream of water. As the silk 
is very liable to take the colour unevenly, 
it is necessary to dye it in small portions ; 
the workman dips each hank separately, 
and when he has turned it once or twice in 
the bath, he wrings it strongly over it, and 
airs it to turn the green colour to a blue ; 
when the green is thoroughly changed, he 
throws it into some clear water, after which 
he wrings it several times with the pin. 
Care must be taken that the silk dyed blue 
dry speedily. In the winter, and in damp 
weather, it should be dried in a chamber 
heated by a stove, where it should be hung 
on a frame kept in constant motion. When 
tile bath grows weak, a pound of potash, 
an ounce of madder, arid an handful of 
bran well washed, are added. Indigo is 
also put in when it appears to be wanted. 
Some dyers use vats grown weak, to dye 
light shades, but fresh vats give a more 
beautiful and permanent colour. 
As indigo alone cannot give a deep blue, 
the silk must be prepared by receiving ri 
ground, or other colour, previous to dyeing. 
For the Turkey blue, a very strong archil 
bath is first given ; and for the French royal 
blue a weaker one of the same kind. Co- 
chineal is used also for the ground of an- 
other fine deep blue, which is more perma- 
nent. Verdegris and logwood are also used 
for a preparatory colour, but produce a 
blue that is not permanent. It might be 
rendered more lasting, by making the shade 
lighter than the intended in this bath, after- 
wards dipping it in the archil bath, and 
lastly in the blue vat. 
When raw silk is to be dyed blue, that 
which is of a white colour should be chosen. 
It should be thoroughly soaked in water, 
and afterwards put into the vat in separate 
hanks, in the same manner as the scoured 
silk. In general, raw silk takes the dye 
more readily ; wherefore, when it can be 
done, the scoured silk is put into the bath 
before it. If raw silk requires archil, or 
the other grounds mentioned, it should be 
treated as directed for silk in general. 
The solution of indigo in sulphuric acid 
is also used for silk ; the colour called Eng- 
lish blue is produced by it. To give silk 
this colour, it is first dyed a light blue, and 
then dipped in hot water, washed in a 
stream, and afterwards left in a bath made 
with the sulphate of indigo, to which a 
little tin has been added, till the proper 
shade is obtained, or the bath exhausted. 
The silk, before it is put into this bath, 
may be dipped in a solution of alum, in 
which it should remain only a very short 
time. Silk dyed in this manner, is free 
from the reddish shade given by the blue 
vat, and from the greenish cast of common 
Saxon blue. 
Of dyeing Cotton and Linen blue. 
The vat for dyeing cotton and linen blue, 
should contain, according to M. Pilenr 
d’Apligny, about 120 gallons. The quantity 
of indigo used is generally from six to eight 
pounds. This indigo, after being pounded, 
is boiled in a ley drawn off clear from a 
quantity of lime equal to the indigo, and 
double its weight of potash. The boiling is 
continued till the indigo is thoroughly pe- 
netrated with ley, which should be carefully 
stirred all the while. 
During the boiling of the indigo, an 
equal weight to it of quicklime is to be 
slacked ; about twenty quarts of warm wa- 
ter are added, and in this is dissolved sul- 
phate of iron, twice the weight of the lime. 
When the solution is compleated, the liquor 
is poured into the vat previously half filled 
with water. To this the solution of indigo 
is added, and the rest of the ley not used in 
boiling it. After this the vat must be filled 
up to witliin two or three inches of the brim, 
and be raked two or three times a day, till 
it is fit for dyeing ; which generally happens 
in 48 hours, or sooner, according to the tem- 
perature of the air. Some add to this vat 
a little bran, madder, and woad. 
In the process used at Rouen, which is 
simpler, 20 pounds of indigo, macerated for 
a week in caustic ley, which will float an 
egg, are ground in a mill ; three hogsheads 
and an half of water are then put into the 
vat, and afterwards twenty pounds of lime. 
When the lime is thoroughly slacked, the 
vat is raked, and thirty-six pounds of cop- 
peras are put in. When the solution of this 
is complete, the ground indigo is put in 
through a sieve. On the same day it is 
raked seven or eight times ; and after having 
stood 36 hours it is fit for dyeing. 
Bergman recommends a still simpler 
bath, composed in the proportions of three 
drams of powdered indigo, three drams of 
copperas, and three drams of lime to two 
pints of water. This being well raked, 
