PLATINUM PAPERS.
The simplicity of platinum printing will prove a revelation to the amateur photographer who imagines that the process must be difficult because so much employed by advanced workers. As a matter of fact, platinum printing presents no more difficulties than the ordinary blue print process so familiar to the novice.
With the exception of carbon, where any colored pigment may be used, no printing process affords so wide a range in tone value, from a pure velvety black down through all the intervening tones to a shade scarcely darker than the pure white of the paper support. It is this ability to preserve the most delicate half tones that affords the charming atmospheric effect so evident in all good platinum prints.
Platinum prints are absolutely permanent, consisting of a deposit of metallic platinum on a pure paper support, and a properly manipulated print will retain its quality so long as the paper support itself exists.
Platinum paper does not demand a negative of special qualities, a negative that will yield a good print on any paper will answer equally well for platinum.
The fact that platinum paper is a semi-developing out paper, and that the image is only partially visible when printing is complete, has lead many to believe that much experience is necessary to judge of the proper printing depth. As a matter of fact, a few trial exposures with negatives of varying density will afford all the experience necessary and the making of prints of proper and uniform quality becomes a simple matter.
All platinum papers are exceedingly sensitive to dampness and for this reason are packed by the manufacturers in sealed cans or tubes, each package containing a small piece of asbestos saturated with calcium chloride to absorb any moisture in the tube.
Platinum paper will keep for months in a cool dry place, and in warm climates, if not for immediate use, is best kept in a refrigerator.
As platinum paper is capable of rendering the slightest half tone it is naturally quite sensitive to light, much more so than the gelatine and collodion printing out papers, and should be handled in a subdued light, not out of doors or close to a window.
When printing, remove only sufficient paper from the tube to fill the frames in immediate use, packing away the remainder as received and placing the cover on the can or tube.
In printing, the paper is placed in contact with the negative in the printing frame in the ordinary manner and exposed to daylight, direct sun light will do no harm and is preferred to shade printing by many prominent workers.
The back of the frame may be opened to note the progress of printing, but in so doing turn your back to the window to avoid sunning the print.
Moisture must be guarded against as it is the greatest enemy of plati num paper, and to secure clear brilliant prints, the paper, printing frame and negatives must be absolutely dry.
In taking up platinum printing, follow the manufacturer's instructions exactly.
When the manipulation has been fully mastered, certain modifications will suggest themselves for special purposes.
The temperature of the developing bath has a decided influence on both the tonality and the color of the image.
Generally speaking, the colder the bath, the colder the image, and the warmer the bath, the warmer the image, all this of course, within reasonable limits as a bath exceedingly cold or hot will be apt to produce mealy flat prints.
Damp paper will yield a print of a brownish black color, with a tendency to meatiness.
Platinum prints may be toned in various ways.
The most common is the " Uranium " which changes the color to a rich-brown or red-brown. The ordinary uranium intensifier may be used for this purpose, the print simply being immersed in it for a time.
An excellent method for uranium toning is given by A. Horsley Hinton: For use take oz. of each, Nos. t, 2 and 3, and 25 ounces water.
A finished unmounted platinotype print, thoroughly cleared from all iron salts, is placed in a flat dish and flooded with the above solution and the dish rocked continuously.
The color of the print will gradually change, the toning should be carried on a little further than when the desired tint has been reached, as the picture will dry out a little colder in color than it appears in the toning bath. It is now brought into a dish of water containing a few drops of glacial acetic acid. The water must not be alkaline, as it would dissolve the uranium compounds deposited on the print and thus change its color again. This property of alkaline water may be made use of in case the desired color of the toned print is unsatisfactory, and one wishes to get it back into its original condition.
It has, as yet, not been conclusively proven that platinum prints treated with uranium are permanent.
It is possible to control this image during development and to make various changes in the various tones of the picture.
This can be accomplished by using the glycerine method, referred to in the platinotype instructions.
It consists essentially of painting the image by means of the oxalate solution, using a brush for the purpose, the paper having first been exposed to light under the negative in the ordinary way.
The method is so full of latitude, that prints have been produced by its means that look like fine wash drawings.
In short, it will be seen by the various matters referred to in this short resume of the platinotype process, that it is beyond doubt the printing method twr excellence for the amateur.