[pure-silver] Re: Silvery spots on prints
- From: "Nicholas O. Lindan" <nolindan@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Tue, 28 Aug 2007 08:37:31 -0500
"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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