Cj Burnett's Process 1857

"A capital process for many purposes," says Mr. Burnett, "is to float or

steep the paper in a mixed solution of bichromate of potash and sulphate

of copper, as for Hunt's chromotype process.(36) I have mixed gelatine, or

occasionally grape sugar, or both with the solution;(37) but instead of

developing it with nitrate of silver, as in chromotype, wash out the salt

unaltered by light, and develop by floating on a solution of ferrocy

of potassium. The purple red color of the copper salt which now forms the

picture may be modified or changed in many ways,(38) viz., by soaking the

picture, after the ferrocyanate of potassium has been washed out of the

lights, in a solution of sulphate of iron. Solutions of gallic acid,

tannic acid with alkalies of carbonate, may also be employed to modify or

change the color. This process has the advantage that one may regulate

the exact tone (black or useful neutral tint) to the greatest nicety by

the time we allow the print to remain in the iron toning bath."