[pure-silver] Re: Purple-Tinted Negs
- From: "Koch, Gerald" <gkoch02@xxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Thu, 1 Jun 2006 09:48:56 -0400
A simple reducer for dichroic fog can be made from 12 g of thiourea and
12 g of citric acid per liter. From Glafkides, Vol I. It also mentions
using formalin to harden the emulsion before using any solution
containing thiourea. This is probably more active than the acidified
fixer.
Jerry
-----Original Message-----
From: pure-silver-bounce@xxxxxxxxxxxxx
[mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of Eric Nelson
Sent: Wednesday, May 31, 2006 6:59 PM
To: pure-silver@xxxxxxxxxxxxx
Subject: [pure-silver] Re: Purple-Tinted Negs
I'll have to try that dichroic fog remover next time
some dagnab Ilford film comes thru here. Seem to get
it to some degree no matter what developer I use.
I agree testing is a very good thing for reassurance
if nothing else.
Eric
> > --- Richard Knoppow <dickburk@xxxxxxxxxxxxx>
> wrote:
>
> Ammonium thiosulfate fixer (rapid fixer) can
> dissolve
> metallic silver when acid and given long enough. The
> problem
> is mainly for the very fine grains of print images
> but can
> occur with film if enough time goes by.
> Normal fixing times for some films in film
> strength rapid
> fixer is on the order of 6 minutes so the above is
> not
> surprizing. If the film is left in for longer,
> perhaps 15
> minutes, there may be some bleaching.
> When neutral or alkaline the bleaching effect
> does not
> take place. Actually, Sodium thiosulfate fixer can
> also
> cause bleaching but it takes forever.
> An effective bleach for removing dichroic fog can
> be made
> from film strength rapid fixer by adding 15 grams
> per liter
> of Citric acid to it. The film must be watched
> carefully to
> prevent bleaching of the image.
>
> Stacking negatives may show up some tint, perhaps
> in the
> support. I use mostly T-Max, both 100 and 400
> speeds, Tri-X
> 400 roll film, and Plus-X roll film. I do not get
> tinted
> negatives with any of these. I do observe a purple
> tint in
> the used KHCA after treatment of T-Max.
>
> One does not have to rely on such indirect and
> perhaps
> unreliable methods such as a residual tint to
> indicate
> complete fixing. The easiest method is to use the
> Sodium
> sulfide test. It is easy to make up and will give a
> good
> indication of any residual silver in the emulsion.
> Kodak
> used to recommend KRST at 1:9 diultion as a low-odor
>
> alternative to Sulfide. They no longer do. I think
> this is
> because the test works only on well washed film or
> paper.
> The diluted KRST has the advantage of not having the
> rotten
> egg odor of sulfide and having longer shelf life.
> Its easy enough to test for good fixing
> periodically, or
> perhaps better, with every batch fixed. Use scraps
> of film
> or paper to make the test.
>
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@xxxxxxxxxxxxx
>
>
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