Some weeks back an inquiry was made on the list regarding what kind of
surface preparation was needed to prepare copper-clad circuit boards to
receive photographic emulsions (gum as I recall). I suggested off-list to
the person concerned that he should first coat the plates with a 3-4%
gelatin solution and then harden it with formalin or chrome alum. I have
not heard back from the person making the original inquiry but some days
later I acquired some of the same type boards and coated them with a thin
coat of gelatin, into which was mixed several ccs of formaline. The plates
looked great at first, with shiny copper and a very thin, clear coat of
gelatin. The next morning, however, they had all turned black. My first
thought was that some kind of reaction had taken place between the formalin
and the copper, but upon recoating with gelatin with no formalin, the same
blackening of the plates took place.
I found that a little Sulfuric Acid strips the gelatin and returns the
plates back to a nice shine so I at least back to home plate.
Sandy King <sanking@hubcap.clemson.edu>