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.
Pink whites are caused by not having the gold bath alkaline enough. Yellow whites may come from prints not being toned far enough in the gold bath. Yellow whites may come from trying to wash prints in running water, between gold and platinum baths or between platinum bath and hypo. This will not do. Prints must be washed by hand and the water changed.
Weak looking prints very often come from not printing dark enough. Try three prints, one as you have been printing, the second a shade darker, the third darker still; tone them all out, select the best and you have the depth to print. Weak looking prints more often come from improper toning in the gold bath than any other cause. Always tone in the gold bath until the shadows are a warm brown (for olive tones). If your whites have cleared and are in danger of bleaching, add more alkali to hold back the whites until the shadows tone. Never take them out a brick red in the shadows. If you do, you are in danger of having weak, muddy shadows and a dirty olive tone out of the platinum bath. If you desire rich, strong shadows out of the platinum bath, you must have rich, strong shadows out of the gold bath. Weak shadows are also caused by not using the salt in the gold bath.
Slow toning in platinum bath is often caused by not using the proper kind of phosphoric acid in making up the platinum toning solution. Only use 50 per cent or U. S. P. phosphoric acid. You cannot be too careful. Too slow toning in the platinum bath is very often caused by the water which you use, for very alkaline water precipitates the platinum. See remarks on the water on page 129. Rubbed places on the face of the prints which do not show until the prints are dried, are caused by rubbing the face of the prints on the bottom of the tray during washing and toning. When you have this trouble, handle the prints face up.