From: Judy Seigel (jseigel@panix.com)
Date: 06/23/02-03:10:45 PM Z
On Sat, 22 Jun 2002, S Wang wrote:
> .... What bleach do you
> use for bleach-and-redevelop?
This has already been answered by several folks, but if I may be
permitted to say so, at too high a level for me. That is, if I didn't have
a pretty good idea already, I wouldn't have followed. So here is my rule
of thumb -- I trust it will be corrected if wrong:
The bleaching agent isn't the critical ingredient -- it's what you use
with it.... the salt and the acid. If you add a salt like potassium
bromide or sodium chloride (usually in equal parts to the bleaching agent)
you get a silver halogen (OK, if you insist, rehalogenate) with
hydrochloric acid, not sulfuric. (Who remembers the other rehalogenating
acids -- acetic? An alkali? I did it with lead, too, but don't remember
details.)
Depending on ingredients, result is silver bromide, silver chloride, or
even iodide, I suppose. (And a neat way to make a silver chloride
printing-out paper from a regular bromide paper -- use a bichromate for
the bleach, with sodium chloride.) With sulfuric acid, the image will,
as noted, dissolve away.
For bleaching agent, BTW, I've used copper sulfate, potassium dichromate,
and potassium ferricyanide, plus I think a couple of others I forget now.
But in my experience from many tests (and the consensus of folks who've
tested similarly) that business about the different contrast ranges of
different ratios of Farmer's reducer is baloney. If you expose identical
21-steps & bleach them, then chart the curves, they will be PARALLEL. THE
ONLY DIFFERENCE IS THE LEVEL OF DENSITY AT WHICH THEY START & END.
The persistence of these Farmer's Reducer "formulas" as part of the canon
is yet ANOTHER testament to the power of belief over observation (just
like something I'll call here for delicacy's sake the PA-GPRT). It's
possible that once upon a time it worked, but it don't now. However the
R15 does change the curve, and very dandy it is too... (as discovered by
someone whose name escapes me now, & revealed in the old CCDR -- or was it
CDR&C? -- magazine, or revealed to *me* there).
There is a great deal of latitude in bleach and redevelop -- you can
reduce, intensify, "harmonize," change tone etc., but again in my
experience, it operates differently in different films, and timing is
critical. Which is to say, uneeda test strip or 2.
> ...It appears that the chromium
> intensifier formula posted by Judy may be a good one to try. I assume
> that you can control and hold back redevelopment, so as to make it a
> reductive instead of an intensifying process.
That's the principal of the "harmonizing reducer," that is, you develop
back only partway, then fix, to cut down the overall range. But IME, the
way they tell you to do it -- by eyeballing the level of redeveloped
silver halogen -- is also baloney. It's EXTREMELY deceptive visually, or
is to us mere mortals. I made it work by sacrificing one frame and getting
the *time* of redevelopment from that... but even then it came out a bit
weak: Intensifying with selenium after that helped -- but Sam, are you
sure you want to live THIS dangerously ? Isn't a gum print enough thrill
of risk for you?
Judy
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