From: Christina Z. Anderson (zphoto@montana.net)
Date: 06/16/03-06:41:14 AM Z
>
> Chris, have you tested the lemon juice gambit? I confess some
> skepticism... that is, when I first noticed that different gums had
> different speeds, I tried to correlate with pH and found ZERO connection
> -- although admitedly I never added tried lemon juice.
> However I have tried several other special additives of gum printing, like
> mixing in -- as I recall it was magnesium sulfate -- and stuff like that.
> Zip. Nada.... All of them.
> J
Judy,
Haven't tried it because haven't felt the need to increase the speed of
gum, although if I remember someone on this list has--Keith G maybe? I
can't imagine that lemon juice would have any other properties except
acidity that would contribute to the mix, so your testing of different pHs
might be enough to disprove it, however I did get a pH wand so I should
fiddle with that and test my egg fart gum. Unfortunately, it is mixed with
powdered pigment (the other colors I have are tube pigment) and I would have
to mix a whole new batch of pigmented gum to test it side by side and get an
even remotely usable result.
How much pH difference was there between the gums? What did you finally
figure your speed difference was due to? How much speed difference are we
talking about? Were the gums thicker or thinner and did that contribute?
I have only used two gums--Daniel Smith and the one I mixed from powder
from Daniel Smith and then the Photographer's Formulary powder so I don't
have any sort of wide experience with gum brands. Oh...no, I did break down
one time and use that little jar of W+N when I ran out.
I should clarify that the lemon juice was for insolubilizing the gum,
or hardening it without exposure, so that there would be "more stability to
the halftones" (Demachy). It is used to counteract the "excessive
solubility of freshly prepared paper and lessen exposure..." Lemon juice
will allow "...slower and surer development..."
He also talks about insolubilization of the gum occurring without light
that happens with "..."old gum that has become acid by fermentation". Seems
both provided him much the same outcome.
The only thing I can think of is to test this method with a bulletproof
neg (I have one that has backlit windows in it behind the
subject--unprintable, really) but even then my puny result will probably be
anecdotal and end up with the proverbial disclaimer YRMV.
Chris
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