U of S | Mailing List Archive | alt-photo-process-l | Re: Dark reaction of gum coating

Re: Dark reaction of gum coating

Hi Listers,

I'm curious if anyone who prints with gum emulsions can say if they have
actually encountered dark reaction. And if so under what circumstances did
that occur?
My experience is a lot like Christina's, but more extreme (this IS New York). That is, in winter when humidity in the studio is in the 30s (average), and temperature about 70 F, coated paper will keep in the dark for a few hours (that's not saying it won't print if kept longer, but changes are probably apparent).

In summer, RH may average in the 60s, and (if the AC isn't on) temperature around 80 or 82, 15 minutes delay in exposing/developing invites fog, or at least enough dichromate stain to require clearing, which I don't usually need.

I'd say it's neither factor alone as much as together. My feeling, BTW, is that putting a coated print in a black envelope with a weight on top (no air) extends the safe period, tho I never tested that specifically.