This section is from the book "Modern Photography In Theory And Practice", by By Henry G. Abbott. Also available from Amazon: Modern photography in theory and practice: A hand book for the amateur.
Aristo platino paper should be printed plain, as a gen-eral thing. Print until the high lights are well tinted. Pay no attention to the shadows, no matter how much they bronze. Wash through six changes of clear water, handling prints over each time. In washing paper, there are two things we must eliminate, the free silver and the keeping chemicals and unless prints are thoroughly prepared for toning, they will not tone thoroughly and evenly. When prints are thoroughly washed, tone in the fol-lowing bath, to a purple, not a blue:
Water..................... 60 oz.
Salt............................. 60 gr.
Chloride of Gold..............1 dram.
Borax enough to turn red litmus paper blue in 3 or 4 minutes.
The gold toning bath should be made up from one to two hours before use. Add enough gold so the bath will tone in from six to eight minutes. Do not run the bath too strong, as the print will tone before the whites clear up. If prints show bleaching in the whites, add a little more alkali. An acid toning bath bleaches out the detail in the whites and also makes pink whites in the finished print. If the bath is too strong in alkali it gives yellow whites.
The character of platinum tones is controlled in the gold bath. If prints are taken from the gold bath a chocolate brown, they will make beautiful olive tones. Prints toned to a purple will make black tones and prints toned to a blue will make blue-black tones. By bearing this in mind, it is possible to get any tone desired. Always, in every case, tone far enough in the gold bath to thoroughly clear the whites. After toning, throw prints into the clear water until all are toned.
Wash prints in three changes of clear water by handling them over. Do not try to wash by placing in running water. It will not do it. It is very important to wash prints thoroughly after they come from the gold bath, to remove any free gold that may be on the prints, as gold precipitates platinum and unless prints are well washed, the platinum will be precipitated on the bottom of the tray and not on the print. Again, never use the regular gold toning tray for platinum bath, as all such trays have more or less gold deposited on bottom and sides and this will precipitate your platinum also. It will not only waste platinum but prints toned through both baths in the same tray will tone down to a muddy blue-black and if kept in long enough, the whites turn yellow. The Platinum Toning. When prints are washed, tone in the following bath: Water, sixty ounces; platinum, three to five drams. Add platinum enough to keep speed of bath from eight to fifteen minutes. The great mistake that photographers have made in toning Aristo-Platino with platinum is, they have not toned long enough in the plat-inum bath. When prints first go into this bath, the whites become muddy but in a short time the whites commence to clear up and by keeping prints in this bath until the whites are thoroughly clear and every trace of brown or purple is out of the deepest shadows, by looking through the print you will get most beautiful effects. Do not be afraid of leaving them in the platinum bath until the desired color and richness you wish is obtained.
When prints come out of the platinum bath, it is very important to wash them thoroughly through three changes of water before fixing, because the platinum bath is extremely acid and it is absolutely necessary to wash it out of the prints. If you do not, you carry it into the hypo and produce sulphuration and yellow whites. This is the reason that all hypo baths containing lots of alum or acid hardeners are dangerous, as this acid releases the sulphur in the hypo and produces sul-phuration in the print that will ruin them sooner or later.
After prints are washed, fix in plain hypo, eighteen grains strong, hydrometer test, for fifteen minutes and then wash by hand through two or three changes of water before placing them in running water one hour. Always mount with good fresh paste and lay out to dry quickly. When dry run through a cold roll burnisher, if you have one, to straighten mount. One-half the old platinum bath with one-half fresh bath added and used over the next time, makes richer tones than a new bath.
Any red spots on platino paper can be removed by rubbing some of the stock platinum solution on the spot with the finger as the print goes in the platinum bath. The spot darkens and the rest of print tones up to it. There is no necessity for losing prints from red spots.