AMERICAN PLATINUM PAPER.
In the production of the American Platinum Paper two very serious defects in the platinum paper heretofore manufactured have been overcome. First, solarizing in shadows; second, the fuzzing or abrading of surface by handling. The manipulation of this paper is very simple, and with a reason able amount of care there should be no difficulty in obtaining good results. The instructions, although simple, must be followed in every detail if the best results are desired. This paper will keep in good condition for a long time if not exposed to heat or dampness. The unprinted paper should be stored in a cool, dry place. When paper is removed from the tube see that the sheets not intended for immediate use are returned to the tube with the package of preservative, and the tube carefully sealed with the tape. If the tube is allowed to remain open, or the paper removed from the tube several hours before using, the effect of damnpess will be noticed in the lack of strength and brilliancy in the prints. Dampness will also cause high lights to develop gray instead of pure white.
Although not absolutely necessary, it is advisable to use thin rubber pads in the backs of printing frames, especially in those sections of the country where the atmosphere is full of moisture. See that negatives and pads used in printing frames are perfectly dry, or the result will be the same as when paper is exposed to dampness before printing. In handling paper, care should be taken not to expose it to strong light Put paper on nega tives and examine prints in weak daylight or artificial light. Care should always be taken not to touch the sensitized surface of the paper with the fingers. This is very important where the hands perspire freely.
Print until the image is visible in all parts, although weak and only faintly outlined in the stronger portions of the neg-ative. The exact depth of printing can only be determined by a little experience. When printing in bright sunlight, use one thickness of tissue or ground glass over the negative. Print weak negatives in the shade or use several sheets of tissue over the frames.
If prints are not to be developed immediately after printing place them in a tube with a package of preservative and seal the tube carefully.
The developer is simply neutral oxalate of potash and water; three ounces of neutral oxalate of potash dissolved in twelve fluid ounces of water. If tones more on the blue-black are desired, use the following developer: Water, ten ounces; oxalate of potash, one ounce; phosphate of potash, one-half ounce. In preparing de\ eloper containing phosphate of potash, always use warm water, as this chemical does not dissolve freely in cold water. Any amount of the developer may be made up and set aside for
future use, but should be kept in a well-stoppered bottle. Use sufficient developer to cover the bottom of the tray at least one-half inch deep. Develop prints face up. By sliding prints under developer face up, air-bells are avoided and the development may be closely watched from the start.
Development, as a rule, only requires from twenty to thirty seconds, but it will do no harm to leave a properly exposed print in the developer a full minute. Prints from strong negatives are very often improved in the half tones by prolonging the development a few seconds. Development should be carried on in a weak light. The temperature of developer must not be below 6o° F. Keep up strength of developer by adding fresh stock solution from time to time. A developer which has become overcharged with chemicals from the paper will produce poor results. The development should therefore be watched carefully when using old developer, and if any change is noticed in the quality of prints, a new bath should be tried. Weak, granular prints may result from the use of weak or too cold developer. Rock the tray or stir the developer between the development of prints to prevent markings caused by scum, which forms on the surface of the solu tion. A print which is known to be slightly under-exposed may be saved by warming the developer to ioo° or r ro° F. Developer. which has been used should not be returned to the bottle of stock solution. Have a sepa rate bottle for old developer and do not allow it to stand in a strong light. When using old developer, pour off the clearing solution carefully, so as not to disturb the sediment which settles to the bottom of bottle.
As soon as prints are fully developed they are placed face down, directly into a clearing bath of muriatic acid and water; one ounce of muriatic acid C. P., to sixty ounces of water. The quality of acid used is of much importance. It should be chemically pure, as ordinary commercial acid will cause yellow prints. Prints should have from three to four changes of acid clearing bath, allowing them to remain in each bath eight to ten minutes and keeping them separated. The last acid bath should be as clear as pure water, showing no yellow tint. This clearing of prints is very important, as permanent results depend on removing all the unacted-on chemicals from the paper. A properly treated platinum print consists of nothing but metallic platinum and paper. After clearing, prints are washed about one-half hour in running water. If not convenient to wash prints in running water, give them eight to ten changes in a tray, separating them well each change.