DYEING. 
a particular kind of clay has been diffused, 
that uniting with the oil, renders it soluble 
in tire water. ' 
Of Silk. 
Silk is naturally coated with a substance, 
which has been considered as a gum, to 
which it owes its stiffness and elasticity; 
that which is most commonly met w'ith, 
contains besides a yellow colouring matter. 
Most of the purposes for which silk is em- 
ployed require that both these substances 
should be removed, which is effected by 
scouring it with soap. 
The scouring ought not to be so com- 
plete for silks which are to be dyed, as for 
those which are intended to remain white, 
and a difference ought to be made accord- 
ing to the colour the silk should leave. 
This difference consists in the quantity of 
soap employed ; for common colours the 
silk is boiled for three or four hours in a 
solution of tw'enty pounds of soap for every 
hundred of silk, taking care to fill up the 
kettle from time to time, that tlrere may 
be always a sufficient proportion of fluid. 
The quantity of soap is increased for those 
silks which ar’e to be dyed blue, and more 
' especially for those which are to be scarlet, 
cherry colour. See. because for these colours 
the ground must be whiter than for such as 
are less delicate. 
When silk is intended to be employed 
white, it undergoes three operations : First, 
the hanks of silk are kept in a solution of 
thirty pounds of soap to the hundred weight 
of silk, which ought to be very hot, but 
not boiling. When the immersed part of 
the hanks is freed from the gum, they are 
turned upon the skein sticks, that the parts 
not before immersed may undergo the 
same operation ; they are then taken out of 
the kettle,. and wrung out according as the 
operation is completed. 
In the second operation, the silk is put 
into bags of coarse cloth, five and twenty, 
or thirty pounds in each bag, which is 
called a boiling bag. In these bags it is 
boiled for an hour and a half in a bath of 
soap, prepared like the former, but w'ith 
less soap, taking care to keep tlie bags 
constantly stirred, that those which touch 
the bottom of the kettle may ndt receive 
too much hegt. 
The third operation is intended princi- 
pally to give the silk a slight cast, to make 
the white more pleasing ; from wlrich it de- 
rives different names, such as Chiai* wliite, 
silver white, azure white, or thread white. 
For tliis purpose a solution of soap is pre- 
pared, the proper strength of w'hich is de- 
termined by its mode of frothing when agi- 
tated ; for the China white, which should 
have a slight tinge of red, a small quantity 
of anotta is added, and the silk is shaken 
over in it till it has acquired the desired 
shade. To the o ther whites more or less of a 
blue tinge is given, by adding a little blue 
to the solution of soap. 
The preparation of silk with alum is ne- 
cessary in all cases, for without it the great- 
est part of the colours applied, would pos- 
sess neitlier beauty nor durability. For this 
operation forty or fifty pounds of Roman 
alum, previously dissolved in warm water, 
is mixed with about forty or fifty pails of 
water. 
After having washed and beetled the silk, 
and wrung it out with the jack and pin, in 
order to separate any soap it may have re- 
tained, it is immersed in the alum liquor 
for eight or nine hours, after which it is 
wrung out by hand over the vat, and washed 
in a stream of water. 
The above quantity of liquor will be suf- 
ficient for one hundred and fifty pounds of 
silk; but when it grows weak, which is 
known by the taste, twenty or twenty-five 
pounds of alum, dissolved as before, must 
be added, and this addition must be re- 
peated, till the liquor acquires a disagree- 
able smell, and then it may be employed 
for stuffs intended for browns, marones, 
and other dark colours, till it has tost all its 
strength. The preparation of silk with 
alum is always made in the cold, because if 
the liquor should be employed hot, the lus- 
tre of the silk is liable to be impaired. 
Of Cotton. 
The several species of cotton differ prin- 
cipally in the length of their filaments, their 
fineness, their strength, and colour. They 
are of different shades, from a deep yellow 
to a white. The darkest cotton comes 
from Siam and Bengal, and is often made 
into stuffs in its natural colour. The most 
beautiful is not always the whitest ; it is 
necessary to bleach it. Processes similar 
to those employed for linen, may be em- 
ployed ; but those in which oxygenated 
muriatic acid has been used, are more expe- 
ditious, produce a more beautiful white, 
and prepare the cotton better (according 
to M. tfe'croisille) for the reception of a 
fine colour in dyeing. 
