Re: gum bichromate

Dan Shapiro (dan@good.stanford.edu)
Mon, 26 Jun 95 11:52:40 -0700

I have found that gum prints flake when the coating is too thick. In
theory, the outer layers harden without establishing a good physical
bond to the paper fibers. Once water gets underneath the crust, the
exposed emulsion lifts off in pieces.

I have this nasty feeling that the process of coating paper with the gum
solution is *the* most sensitive variable in gum printing, meaning that
a small deviation from the "right" thickness causes big differences in
print quality. Or, more to the point, coating is the easiest step to
mess up.

Do others agree? We have talked about the variables in gum printing,
but we haven't really discussed their sensitivity. At the same time,
sensitivity questions make all the difference when you are staring at a
disasterous print and want to know what to do *next*.

Dan Shapiro