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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.

The 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.





Next: H Cooper's Process 1865

Previous: Graphotypy



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