Re: GENTLE BLEACH

From: BOB KISS <bobkiss@caribsurf.com>
Subject: GENTLE BLEACH
Date: Thu, 02 Jun 2005 11:30:01 -0300

> Might you be willing to post a working formula for the "gentle
> bleach" with instructions for use on the list?

I'm too lazy to find my darkroom notebook now, but the formula goes
like this.

15g citric acid
10g sodium metabisulfite
2g disodium edta
70ml 60% ammonium thiosulfate
water to make 1 liter

The source was... i'll find it. it's supposed to be a well known
secret from around 1950, to which i added edta. It probably became
unpopular along with other toners and bleaches because printing papers
changed and also consumers became to prefer fast/easy/cheap
methods. But this formula works.

It's very useful when you have dichroic fog or yellow stain (a few
minutes). It also works as a gentle bleach (about 10-20 minutes).
The solution is clear, so it's best used by bath application. I never
used it with brush application (can't see the solution!).

Most papers made by major manufacturers are well hardened, but if you
use products of small companies, you might want to run a test first to
make sure the emulsion doesn't swell excessively in the bleach and
more importantly in subsequent wash. If it does... find a better
paper. (I don't think alum hardeners in this bleach or fixer would
work very well because citric acid interferes with hardening action of
alum.)

--
Ryuji Suzuki
"Well, believing is all right, just don't let the wrong people know
what it's all about." (Bob Dylan, Need a Woman, 1982)