Tom
While it is claimed that gum platinum prints ninety years ago were made so
that the gum could give good blacks to platinum/palladium prints, I have
always found it difficult to believe as platinum is the medium that
gives the good blacks. That is one reason why I put the platinum/palladium
coat on second so that the gum layer will not hide the rich blacks of the
platinum. Another reason is to give the gum print delicacy of detail in the
highlights, say white lace on a pale background, which is very difficult to
achieve with gum by itself. That delicacy would also be obscured if the gum
were put over the pt/pd.
Terry king