From: Judy Seigel (jseigel@panix.com)
Date: 10/04/01-07:34:11 PM Z
On Thu, 4 Oct 2001, Peter Marshall wrote:
>
> Finding my old notes is likely to be a problem, but I think it is in the
The rule is, NEVER put anything "away." My "mordancage" folder sat under
the black loose leaf notebook on the darkroom desk for 10 years. Sometime
last year I consulted it -- when we had this discussion on list for 2nd or
3rd time. And then I must have made the mistake of "filing" it. Odds are
it will surface again, but meanwhile.... this from memory:
The "mordancage" in the old literature & as practiced (just to add
confusion) by a man named Mariage is somewhat different from what is being
CALLED mordancage by a bunch of upstarts like Jon Bailey & Chris Anderson
& Elizabeth(?) Opalnik & for all I know Jean Paul Sudre. THEY call the
REAL mordancage "etch bleach," but that's something else actually.... or
several somethings else according to which hobby magazine you read, and of
no concern here. Are you still with me?
Well,the REAL mordancage uses a bleach formula on a print that is
DEVELOPED but NOT FIXED. Therefore there is metallic silver (the black
image) as well as remaining silver halide (unexposed original emulsion not
yet washed away).
In this formula, the copper sulfate with hydrogen peroxide (and for all I
know you could do it with copper chloride instead) and an acid will
attack and dissolve BLACK SILVER only, leaving the non-metallic
undeveloped silver halide intact. My formulas all called for a bath in
hot water after the bleaching -- you felt with your fingers until the
silver was raised and starting to come off, then swabbed it away with
cotton, which took more or less time depending on your personal virtue,
heat of the bath, strength of the bleach, position of the planets, etc.
Then you had a print with raw uncoated paper where there had been image,
and silver halide where there hadn't. At this point you exposed the
undeveloped part and developed again, which gave you a REVERSAL of the
original, no need to fix. Since I solarized my original, which often
reversed, I could end up with a positive, or near positive.
The point I am about to make now about COPPER SULFATE is that it does
different things with different ingredients. With the peroxide, it
destroys silver. But you could see that if it hasn't worked, increasing
the proportion of copper sulfate would make matters WORSE -- diminishing
the ratio of the peroxide would very likely compound the problem. Possibly
more or stronger peroxide, or maybe a hot bath, or better incantation
would have worked, but your latterday "mordancage" is not known to me, so
I hazard no further guess and continue about copper sulfate...
Bleaches based on copper sulfate (as opposed to the more usual potassium
ferricyanide, or other) are classics of bleach-and-redevelop toning,
and/or bleach-and-redevelop intensification. In my file (the little drawer
which was NOT misplaced) I see I have 22 different versions. I used them
for at least 10 years with my plating-out toner, and they seemed more or
less foolproof. These consist of copper sulfate, an acid (or occasionally
an alkali) and a salt which is usually either potassium bromide or sodium
chloride.
I was told by a chemist that you don't need the acid, it just speeds
things up, and indeed the bleach did work without acid, but I found that
different acids made slightly different colors in subsequent toning. I
used mostly hydrochloric, but acetic, sulphuric and nitric also worked --
the only one that was problematic was oxalic, which precipitated out. What
I'm getting to in a long-winded way (it's always easier to write long than
short) is that the SALT with the bleach brought your photograph back to a
halide again, instead of destroying the silver. You got silver bromide or
silver chloride, or chlorobromide with the two mixed (or so I
hypothesized). In other words, you bleach out the photograph & then
redevelop in a different contrast, or different color, or ....whatever.
The 3rd use of copper sulfate as bleach that I know of is slightly
different -- as a tanning developer for bromoil. This has your ordinary
bleach ingredients plus potassium dichromate. In some related or unrelated
way it tans (hardens) the parts that have silver so they won't swell in
water and will take the paint hopped onto them... In fact I used bromoil
bleach as a toning bleach once or twice & it worked, but was more trouble
(stain had to be cleared) & no benefit, so I gave it up.
There are probably more uses of copper sulfate in photography I don't know
or have forgotten, but its main use (& probably reason it's available for
only $7 per pound) is in gardening, where it's called blue vitriol and
sold in nurseries -- the garden kind, not the baby kind.
best,
Judy
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