The Uranotype

This process, devised by J. Wothly, in 1864, did not receive from the

photographers the attention it merits, as it is always the case when a

process is patented, and can be replaced by another equally practical

which is not. It gives pictures of a very good tone, which are quite

permanent; we have some made in 1866, which are suffered no change

whatever, they seem to have been printed from yesterday.

first process given by Wothly does not appear to be complete. It has

been well described by H. Cooper and a gentleman who signs by the initial

letter X.

The process published in 1865 by Wothly is as follows: A sheet of paper is

sized by brushing with a paste made of 24 parts of arrowroot in 500 parts

of water, to which are added a few drops of a solution of citric or

tartaric acid, then coated with a collodion consisting of 100 cubic

centimeters of plain collodion, a few drops of oil of turpentine and 30

cubic centimeters of the following sensitizing solution:

Nitrate of uranium 30 to 90 parts

Chloride of platinum 2 parts

Alcohol 180 parts

The time of exposure is about that required for paper prepared with silver

chloride. The image is bluish-black but weak. After washing the print is

immersed in a solution containing 0.5 parts of chloride of gold for 2,000

parts of distilled water, and then fixed in a bath of sulphocyanate of

potassium, which tones the image blue-black.

It may happen that the proof is slightly tinted red. This arises from a

small quantity of lime in the paper which forms uranate of calcium.

To prevent the proofs turning yellow, it should be washed in an

exceedingly weak solution of acetic acid.

If, after exposure, the print is immersed, without it being washed, in the

gold bath, the image becomes rose-red, but the whites remain pure. The

effect is peculiar.