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.
Black Spots On Prints While In Platinum Bath. This is due to some foreign chemical, or matter, getting into the toning bath. In preparing your solution never use a graduate which has been used for a plate, or paper developer, as the least bit of metal, iron, etc., will produce black spots. Filter the water used for the gold bath and platinum solution, as iron rust from the water pipe will also cause these black spots.
Toning Red Out Of Prints In Platinum Bath. If your platinum bath has been properly prepared, and is acid, you will experience no trouble in toning the red from the deepest shadows. Only when the platinum bath is alkaline, which causes the platinite to become precipitated, will you meet with this difficulty.
Prints Too Brown After Being Toned In Both Baths. If the prints are toned too far in the gold bath there is nothing left for the platinum bath to tone and, consequently, they will turn brown. Insufficient washing between the toning baths and fixing bath will also cause brown tones. Hypo bath being acid is apt to turn the prints brown, as sulphurization is sure to set in.
Unable To Obtain An Olive Tone. This will occur if you carry your toning too far in the gold bath and not quite far enough in the platinum bath.
Difficulty In Obtaining Black Tones. Prints toned to a blue-black in the gold bath will cause blue tones in the platinum bath. Prints toned to a purple can be toned to a black in the platinum. Prints that are toned to a deep chocolate-brown in the gold bath will make beautiful olive-black tones when toned in the platinum bath.
Bronzing. Bronzing in the shadows is generally caused by not toning the shadows properly in the gold bath, and not far enough in the platinum bath afterward.
Poor Tones. While at times this may be due to the product that you are using, it is generally caused by one or all of the following reasons:
283. (b) Using too strong a gold bath, toning in a few minutes, thereby producing a surface tone. This surface tone will cut off almost entirely in the fixing bath.
284. (c) Insufficient preliminary washing, consequently failing to remove the preserving chemical, causing the toning bath to become acid.
285. (d) Platinum bath made up with a strongly alkaline water which was not previously acidified, thereby precipitating the platinum.
286. (e) Not neutralizing or acidifying the prints after coming from the gold bath and before placing in the platinum bath; consequently carrying considerable alkali into the platinum bath, thereby precipitating the platinum.
287. (f) Carelessness in preparing the hypo bath, guessing at it, as it were, with the result that the strength of the hypo might vary from 30 to 50 degrees.
288. (g) And still another reason is printing too lightly.