William Willis Patent 1873 #2011

An Improved Process of Photo-chemical Printing

British Patent #2011, 5th June 1873, William Willis Jnr

Specification

This invention has for its object improvements in the chemical treatment of the surfaces of paper, wood and other suitable materials employed for receiving images from photographic negatives or from any other object that may be interposed between the light and such prepared paper or other surface.  For this purpose according to my Invention I apply to surfaces of paper, wood, and other suitable materials (by either one or more coatings) solutions of simple or compound salts of platinum, iridium, or gold, or a mixture of such salts.  After this has dried I sometimes apply another coating of a solution of a salt or salts of other metals.  I then coat the material again, using a solution of ferric oxalate, or tartrate, or a combination of these salts with others, and dry again.  I then expose the coated surface to light under a photographic negative or other suitable object until a faint brown image appears;  after this I apply to the coated surface a solution of the neutral oxalate of potassium or other suitable oxalate, which speedily changes the brown tints to black ones.  I then wash the surface thus treated for a short time in a dilute acid, and finally wash in water ;  but I sometimes immerse the surface in a solution of chloride of sodium, or hyposulphite of sodium, or other suitable salt before giving it a final wash in water.

The following are several examples of the operations and manner in which I employ some of the chemicals above referred to in carrying out my Invention into practice :-

First Operation.—I coat paper with a solution of the chloro-platinate of potassium containing 10 grains of the salt to 1 oz. of water.  After drying the paper I coat it again with a solution of the nitrate of lead, 40 grains of the salt to 1 oz. of water, and dry it again.  I then coat it a third time with a solution composed of ferric oxalate, 60 grains to 1 oz. of water, with as little oxalic acid as is sufficient to render the fabric [IL: ferric] oxalate soluble.  I then dry the paper and expose it to light under a negative.  On removing it from the negative I float it face downwards on a hot solution of potassic oxalate.  I then wash it in a weak solution of oxalic acid, then in plain water, and finish by immersing it in a solution of hyposulphite of soda followed by a slight wash in plain water.

Second Method.—In this method I proceed as in the first, but substitute an 8 grain solution of nitrate of silver for the nitrate of lead, and after removing the prints from the weak solution of oxalic acid I finish them by an immersion in either a strong solution of chloride of sodium, or in a weak solution of that salt, followed by a weak solution of ammonia, supplemented in both cases by a wash in plain water.

Third Method.—I coat paper with a solution of platonic bromide, 12 grains to 1 oz. of water, and dry.  I then coat it with a strong solution of ferric tartrate, and dry.  I next expose this paper to light under a negative, and afterwards float it face downwards on a hot solution of potassic oxalate.  I then immerse it in a weak solution of oxalic acid, and finish by washing it in plain water.

I occasionally vary the proceeding operations, or invert their order, or omit one or more of them.

I would remark that I do not intend to confine myself to the use of aqueous solutions of the chemicals herein-before referred to, as the salts may be dissolved and used in any suitable solvent.

I sometimes mix two or more of the salts used for coating the paper or other surface before application.