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Re: Dichromate and the plate



Sarah,

Sorry, I'm new to gum, but you're absolutely right - the whites were fine,
but there was staining in the pigmented areas.  After soaking some more
(about 6 hours in total), the stain was just beginning to clear, and a pinch
of bisulphite got rid of it in seconds.

That was my third gum print so far, and I thought it a good idea to put #1
and #2 into bisulphite, just in case.  These were made with ivory black and
Indian red and had had much less washing; they had apparently cleared OK,
and showed no further change in the clearing bath.  I don't get it at all,
but I'll clear in future.

I think you'll find an alkaline soak will reduce or undo tanning.  To quote
Clerc on the bromoil process:  "To ensure the proper degree of swelling, it
is usually sufficient to leave the print in cold water for several hours, or
in tepid water (80-95 deg. F) for a quarter or half an hour.  It is also
possible to hasten the swelling with a solution of ammonia (4 per cent to 10
per cent of ammonia), the print being rinsed afterwards in cold water.
Finally, if a transfer press is available, the wet print may be pressed
between two pieces of dry blotting paper, the print thus acquiring, on
re-wetting it, a more accentuated relief, according to the number of times
it is put through the press."

And a brief quote from Southworth & Bentley, on fixing, hardening, washing
and drying:  "Chemical hypo-eliminators are occasionally employed to replace
or expedite washing.  Some of these, e.g. caustic soda, act apparently by
softening the gelatine and accelerating the diffusion of hypo."  They also
say, elsewhere, that Kodak HE-1 softens gelatin (or gelatine, as it was
called in those days!)



Liam