[ 128 ] 
vitriol, by which means the indigo becomes of a 
much more lively colour, and is extended to fuch a 
degree, that it will go very far in dying. 
A receipt for making the beft Saxon blue will, I 
dare fay, be agreeable to many ; I will, therefore, 
give the following, which produces a very fine colour, 
and never fails of fuccefs. 
Mix § I of the beft powdered Indigo, with J 4 of 
oil of vitriol in a glafs body or matrafs : and dlgefl 
it for one hour with the heat of boiling water, fhak- 
ing the mixture at different times; then add § 12 of 
water to it, and ffir the whole well, and when 
grown cold filter it. This produces a very rich deep 
colour ; if a paler blue be required, it may be ob^ 
tained by the addition of more water. The heat of 
boiling water is fufficient for this operation, and can 
never fpoil the colour ; whereas a fand heat, which 
is commonly ufed for this purpofe, is often found 
to damage the colour, from its uncertain heat. 
Indigo, which has been digefted with a large quan- 
tity of fpirit of wine, and then dried, will produce 
a finer colour than the former, if treated in the 
fame manner, with oil of vitriol. 
No one, that I know of, has heretofore made ufe 
of the acid of nitre, in head of the acid of vitriol ; 
and it is by means of the former that the yellow 
colour is obtained : it was neverthelefs natural to ufe 
it, on account of its known property of making 
yellow fpots, when dropped on any coloured cloth. 
The acid of fait does not diffolve indigo, and 
therefore is of no ufe in dying. 
Receipt 
