This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
392. The general manipulation of collodio-carbon paper is practically the same as for other matte surface papers, and the majority of the difficulties are covered in previous instruction. However, a few additional difficulties you may encounter follow:
Eliminating The Free Silver. If you have any difficulty in this manipulation, it is probably because the water is acid. If you find the water does not take on a clear, or possibly very slight milky appearance, neutralize it by adding a small amount of carbonate of soda, which will cause the free silver to wash out more readily.
Shadows Toning Before Whites Are Clear. This will happen if your bath contains too much gold, tones too rapidly, or, if an excessive quantity of acetate of soda has been added. Paper badly discolored from age, or which has been kept in a high temperature, will tone in the shadows before the whites are clear.
Knowing When Prints Are Sufficiently Toned. Practice and close observation only can teach you this. Watch results. Remember that the final tone is almost entirely governed by the amount of toning in the gold bath. If the prints are too red when coming from the gold bath, the resulting tone in the platinum bath will be olive. Toning too far in the platinum bath will produce blue blacks.
Chalky Whites. Generally caused by acid water, or acid hypo. Neutralize the water or the hypo and you will readily overcome this difficulty.
Muddy Shadows. Caused by using too much alkali in the gold toning bath.
Muddy Whites. If prints are not thoroughly washed between the gold and platinum baths and between platinum and hypo bath, muddy whites will result.
Prints Turning Blue In Platinum Bath. If the prints turn blue in the platinum bath, even though they have not been toned too far in the gold bath, it shows the platinum bath is too strong. Reduce the speed by adding water and also warm the bath slightly.
Prints Too Olive In Platinum Bath. If they have been toned to the proper depth in the gold bath when this occurs, it shows that your platinum bath is too weak. Strengthen by adding more of the platinum solution.
Edges Of Mask Are Vignetted, Showing Yellow. This is a certain sign that your gold bath was over-alkaline.
Prints Blistering. Blisters are generally caused by change of temperature in baths or wash waters, and usually appear in the hypo, or immediately after. When you are preparing the hypo bath the fresh hypo crystals reduce the temperature of the water. Putting the prints into this cold hypo bath and from there into the warmer wash water causes blistering. To a great extent, this can be prevented by the use of the salt bath after the hypo bath, as already recommended in the instruction.
404. Whenever the wash water is found to be considerably cooler than the air, the prints are likely to blister when lifted from the water and exposed to the action of the warm atmosphere. Too much carbonate of soda in the first wash water is also liable to cause blistering. When it occurs from this cause it generally shows in the first wash waters before toning. If this is the case, use less carbonate of soda in the wash water. If you experience no trouble with the staining of prints and prints wash freely, use no carbonate of soda at all.
405. It is also claimed that another cause for blistering is gas or air in the water. The presence of gas may easily be detected by simply filling a glass with water directly from the tap. Examine it by holding the glass up to the light. If there is gas present it will show by minute bubbles rising to the surface and clinging to the sides. Water like this should be allowed to stand in a barrel or tub from six to eight hours before using, which will allow the gas or air to pass off.
406. Still another cause, which we believe is the main one, is the use of old paper. Cases have been noted where paper that was old and somewhat discolored blistered so badly when placed in water that the entire emulsion floated from its support (the paper). This has occurred not only on collodio carbon, but with Aristo Platino and almost all other makes of matte surface printing-out paper.