Houdoy's Process 1858

The paper is floated upon a lukewarm solution of gelatine at 5:100, and

when dry, on a bath of uranium at 10 or 15 per 100 of water. After

exposure to the sun the image is developed with a solution of silver

nitrate acidified with acetic acid. The exposure varies, according to the

nature of the negative, from one to ten minutes; it must be long enough

for the image being developed in from thirty to forty seconds. It is then

removed from the silver bath and placed in the following:

Ferrous sulphate 3 to 8 parts

Acetic acid 2 parts

Water 100 parts

In this bath the image takes a great vigor and appears entirely on the

surface of the paper. When the proof has been too long exposed it should

be washed slightly before placing it in the iron bath. Developed, the

image is, generally, of a sepia tone, which can be turned to black by a

solution of chloride of gold, 1:1,000, washing afterwards as usual.