It's really quite simple: fog the paper in direct relation to the uneven
density by giving white light exposure to the back of the paper, in
addition to the normal exposure to the emulsion side. This additional
exposure will give the negative a mottling that cancels out the paper
texture when it is viewed on a light table.
To arrive at the right amount of exposure, I would suggest doing test strip
exposures to both the front and the back, at 90 degrees to each other.
Examine the result on a light table and pick out the smoothest patch.
Paper texture may have its own charm, but it can be minimized by the above
method.
Hope this is useful.
Sam Wang
Professor of Art
142 Lee Hall, Clemson University, Clemson SC 29634-0509
Stmwang@hubcap.clemson.edu