From: Judy Seigel (firstname.lastname@example.org)
Date: 05/10/01-06:44:16 PM Z
> The way I work carbon is that I adjust the strength of the sensitizer to
> the DR of the negative being printed. With a sensitizer of known strength I
> can be sure, for example, that a potassium dichromate sensitzer of 1% is
> good for a negative with a DR of about 1.1, whereas a 6% solution works
> with DR of about 1.6. With sodium dichromate I might measure out 10g of the
> chemical to mix with 1000ml of water for a 1% solution, but if the
> dichromate had previously absorbed a lot of moisture from the atmophere the
> actual equivalent might be only a 1/2% solution, or perhaps even less.
> This would dramatically change the printing qualities of the negative. You
> don't have this kind of problem with ammonium and potassium dichromate.
> I believe the same kind of relationship exists in gum printing but it is
> not so readily apparent to you folks because you work is kind of, shall I
> say, free-hand as opposed to mechanical.
Sandy, there probably /maybe are gum printers who THINK they work that
way, or maybe even do... but as each coat has a different color and hits a
different paper base (changed by previous coats) and in any event is
easily adjusted by changes in development... well, I think life & art have
more rewarding avenues for input of energy.
Exact strength apparently does matter with carbon printing, since you (I
think ) only do one coat, no later modifications) and also (as I
understand) develop is more or less pre-set, no wiggle room... (And note
that even with one-coat gum, development is infinitely variable.) HOWEVER,
if you mixed your na di all at once (let's say you were in a cave in
Carpathia where they only had na di) you'd be working off the same
strength solution & could be as systematic as desired.
More to the point, I myself do NOT like the idea of handling the dry
chemical for each print. That to me is the worst possible "solution."
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