The difficulty with masking negatives is threefold: (1) is the mask thick enough to stop the light; (2) is it so thick that it reduces the pressure on the negative and hence leads to soft spots on your print; and (3) is the edge effect from the mask pleasing?
Various materials may work depending on your process. When I want to make negatives I use non-adhesive rubylith that I bought from a guy on eBay.
If you're using a hand-coated process then an alternative is to mask your paper (before coating) rather than the negative. This can be a little bit fiddly but it works. It's my preferred way for masking with pt/pd.
|