William Willis Patent 1880 #1117

Willis’ Improved Materials for Photo-chemical Printing

British Patent #1117, 15th March 1880, William Willis Jnr

Specification

My present Invention is based partly upon the process of photo-chemical printing described in the Specification of my former Letters Patent, dated June 5th, AD 1873, No. 2011.  By the said process the paper or other surface was coated with a solution of platinum, iridium, or gold, or a mixture of these salts, and sometimes with other salts, and then with ferric oxalate or tartrate.  In practicing the said process it was found necessary to use a salt of lead or of silver, and after exposure to light the said surface was treated with a solution of potassic or other suitable oxalate, but I have now discovered that I can dispense with the lead and silver salts, and by avoiding their use can obtain greatly superior results.  By this improvement all danger of discolouration of the white portion of the prints arising from the use of metals other than iron or platinum is completely avoided.  Moreover this improved process will be simpler that the said former process, and will obviate all liability to failure otherwise from improper exposure or carelessness.

My present Invention comprises paper or other material with its surface prepared and rendered sensitive for photographic purposes by the application of a coating solution containing platinous and ferric salts in such proportions or quantities as are hereinafter specified.  The term platinous is used in this Specification in its chemical sense to distinguish the salts designated by it from those known as platonic salts.

The said Invention also comprises an improved process consisting in first preparing the paper or other surface by the use of the coating containing platinous and ferric salts as hereinafter specified, then exposing it to light under or behind a negative, and then developing the picture by means of my improved solutions or other suitable developers.

The said Invention also comprises improved developing solutions to be applied to paper or other surfaces which have been coated with platinous and ferric salts.

These improved developing solutions may be applied to the paper or other material which previous to its exposure to light has been coated with ferric and platinous salts mixed in the proportions hereinafter specified or in different proportions and with or without the addition of a salt of lead or of mercury.

One distinguishing feature of my present invention is the comparatively large quantity of platinous salt used in the coating of the paper or other material, that is to say, in my present improved process I do not employ less than one and seven tenths (1.7) of a grain of the platinous salt for each square foot of surface to be coated, and I prefer to use a much larger quantity, usually as much as four (4) grains of such salt, and sometimes more, for each square foot of coated surface, whereas in the practice of the Invention described in the said former Specification the quantity of platinous salt used did not exceed two thirds (2/3) of a grain for each square foot of the surface coated.

By the use of such greatly increased quantity of platinous salt in the coating I obtain results greatly superior to those obtained by the process described in my said former Specification.  I also obtain results superior to those obtained by the improved process described in the Specification of my Patent dated 12th July, AD 1878, No. 2800, while obviating the necessity for the addition of a platinous salt to the developing solution as described therein, and thus simplifying the process.

The platinous salt I prefer to employ is the potassic chloro-platinite.  I use this salt in such proportion or quantity that each square foot of the surface will receive, when coated, not less than one and seven tenths (1.7) of a grain thereof, but usually a much greater quantity, that is to say, about four 94) grains of the salt, and sometimes more.  The iron salt I prefer is the ferric oxalate.

The platinous salt and the iron salt may be mixed in the desired proportions, and dissolved in a suitable quantity of water, and then applied to the paper or other surface, or the solutions of these salts may be applied separately.  I prefer to use for the ordinary purposes an aqueous solution containing in each fluid ounce sixty (60) grains of potassic chloro-platinite and sixty (60) grains of ferric oxalate for application to the paper or other suitable surface.  I don not confine myself to this proportion, but may use less or more, according to the result desired to be obtained.  The solution is applied to the paper or other surface by means of a pad of cotton wool or flannel, or the paper may be coated with it by any of the means known to photographers.

The paper thus coated is after being dried ready for use, and after its exposure to light under or behind a negative I apply to it a developing solution containing potassic oxalate or either of my improved developing solutions.  The developing solution of potassic oxalate is made by dissolving one hundred and twenty (120) grains or more of the salt in one fluid once of water.  As soon as the print has been developed by means of this solution I wash it, first in a weak solution of acid, preferably citric acid, and afterwards in water.

I prepare an improved developing solution as follows, that is to say :— I use for this solution the tartrate or citrate of soda, of potash, or of ammonia, or any compound of any of these salts with each other.  Or I use acetate of soda, of potash, or of ammonia or the monoammonic, the diammonic or the monosodic ortho-phosphates ;  I prefer however to use the citrate of soda.  I use one or more of the above named salts or mixtures of these salts, or other salts which will serve the same prupose, alone or mixed with the salts of platinum or of iridium, as described in the Specification of my said former Letters Patent, No. 2800.

I apply the developing solution thus prepared to the paper or other surface coated according to the first part of my present Invention with platinous and iron salts or to the surfaces that have been coated with platinous and iron salts used in proportions different from those specified in the said first part of my Invention ;  I also apply the said developing solution to paper or other surfaces that have been platinous salts, ferric oxalate, and salts of lead or mercury as described in the Specifications of my former said Patents.

I prepare this developing solution as follows, that is to say :— I make a solution containing one hundred and twenty (120) grains of citrate of soda in one ounce of water, of a sufficiently strong solution of either or any of the other salts above specified.  This solution may be applied to the prepared paper or other surface by pouring it over the same, or by immersing the paper therein, or by floating the paper thereon.  It may be applied cold, warm, or hot, but preferably hot.  The strength of the solution may be varied, but the best results will usually be obtained by a strong or saturated solution.  To this solution of citrate of soda or of any or either of the other salts I may, as above specified, add a salt of platinum or of iridium, as specified in the Specification of my former said Patent.  I prefer the potassic-chloro-platinite for this purpose.