In regards to non-silver photo printmaking pH may be a red herring. My
primary interest is Pt & Pd printing and over the years this topic has
come up frequently from our customers. Several have undertaken studies to
determine the paper pH's and such. Bottom line is that the pH is almost
always neutral 7.0 after the print has been made and processed. That is,
all of the yucky acids are washed out in the process. The prime culprits
are the sufites from wood pulp processing and alums in size hardeners.
Since most wood pulp papers (3 hole notebook, newsprint, etc) would not
physically withstand the making of a platinum print, this issue is
largely mute. Insofar as the alum hardeners go, the size and offending
acids go out in the wash.
Any discussion on this matter should be focused on the pH of the paper
AFTER the print is made. As one can see this is quite a different concern
for other paper media such as pastel, charcoal, etching, or drawing.
--Dick Sullivan
Bostick & Sullivan