[pure-silver] Re: Silvery spots on prints
- From: "BOB KISS" <bobkiss@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Tue, 28 Aug 2007 08:41:25 -0400
DEAR NICHOLAS AND JUKKA,
I have just found some RC prints with the same silver spots. I am
not certain these are dichroic fog because they easily wash off with water
while gently wiping the surface of the print with wet cotton under water.
They leave no visible trace behind when the print dries. Dichroic fog seems
to be an integral part of the emulsion which doesn't wash off. I have
recently read (I think in one of Richard Knoppow's posts) that it can be
bleached.
So, Jukka, try carefully re-washing the prints while GENTLY wiping
the surface with cotton.
CHEERS!
BOB
-----Original Message-----
From: pure-silver-bounce@xxxxxxxxxxxxx
[mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of Nicholas O. Lindan
Sent: Tuesday, August 28, 2007 9:38 AM
To: pure-silver@xxxxxxxxxxxxx
Subject: [pure-silver] Re: Silvery spots on prints
"J. Lehmus" <jlehmus@xxxxxxxxxx>
> Now and then I've noticed odd "silvery spots" on my RC prints. The spots
> are of irregular shape, about the size of a fingerprint, and usually
> located on the unexposed area or near the edge of the paper. They are
> metallic silver or pale brown in colour.
> I've noticed that at least the pale brown ones can be
> wiped away from the surface of wet emulsion.
The problem is called dichoric fog or silver redeposition.
The usual causes are too much silver in the fixer, not enough acid in
the stop bath, poorly formulated/wrong/contaminated/exhausted(?)
developer, using a poorly washed fix tray for the developer,
carrying over exhausted fix into the developer and other sins of
commission and omission.
In this case it appears dirty hands leaving chemicals on the
paper is also a contributing factor.
> the spots seem to form when processing the paper face down, and with
> chemicals that are near to exhaustion.
You are most likely using chemicals _past_ exhaustion.
> This is not a problem - it never happens with clean trays
Hmmmm. Cleanliness is next to Godliness.
Considering the processing methods, this is _supposed_ to happen -
if it didn't then something would be wrong.
With fresh chemicals it can be due to too much solvent action - sodium
sulfite - in the developer combined with not enough developing agent.
Old formula fine-grain developers used with TMax style films
are prone to the problem. Newer versions of these developers have
sequestering/chelating agents to bind the excess dissolved silver.
* * *
If you are looking to create this effect there are chemicals on the market
that make silver/mirror prints.
--
Nicholas O. Lindan
Cleveland Engineering Design, LLC
Cleveland, Ohio 44121
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