[pure-silver] Re: What happend?


----- Original Message ----- From: "Breukel, C. (HKG)" <C.Breukel@xxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Wednesday, June 28, 2006 7:47 AM
Subject: [pure-silver] What happend?


Hi,

In my work office I have this photograph on the wall next to my monitor:
It's a B&W print of my kids on Ilford MGIV, RC processed in DS-14. I
usually make rather quickly test prints on 8*10 RC, later I decide which
ones I want to reprint in (sometimes bigger format) FB.

This print has been hanging there for about 4 months and has been
"changing" since 1 month or so. The light gray clouds behind the kids
(and other lighter pars) are changing colour to a yellow /brown, quite
nice btw.

At first I assumed I did not fix long enough, or used exhausted fix, and
accepted as a "badge of shame"..;-).. But than I realized that the white
borders stayed nicely white, as well as other lighter than light grey
stayed white, so here is another phenomena taking place, but what.
Attack of pollutants on the silver image? (it was not toned), or
something else?

There are a few small "splotchy" areas in the grey clouds which stayed
grey, so perhaps nevertheless the fixer?

Best,

Cor

It could still be incomplete fixing. Some methods of agitation will cause more flow at the edges of a print than others. This can also be true of washing. The blotchy effect sounds like insufficent fixing to me.
One way to find out is to test the print using either the sodium sulfide test or the Selenium toner test. The Selenium test is simply a solution of KRST diluted 1 part toner to 9 parts water.
The Sulfide test uses the following solution:

Kodak ST-1 Stock Solution
Water                100.0 ml
Sodium Sulfide         2.0 grams

The stock solution will last about 3 months in a filled, closed bottle.
For use dilute 1 part stock with 9 parts water. The working solution will last about a week.
Place a drop of either solution on a clear area of the print or film. Leave for a minute or two and blot off. There should be no visible stain.
This test fails on prints that have been toned with a sulfiding toner or selenium toner. The selenium test solution works only on well washed film or paper, it fails in the presense of large amounts of hypo. When finished prints are tested this way they should be washed as they would be after toning.
The silver nitrate test HT-2 can be used to test for completeness of washing.
My guess is that this effect is due to sulfiding from incomplete fixing or washing rather than oxidation but it could be either.
To prevent oxidation prints should be toned in a sulfiding toner like Kodak Brown Toner or Kodak Sepia Toner, or treated with KRST in a stong enough solution (1 to 9 or stronger) and for long enough (3 or more minutes) to produce a significant amount of toning of both highlight and shadow areas. Gold toner is also very effective but expensive.
KBT has the advantage of providing significant protection when only partial toning is done to minimise the effect of the toner on image color or density. Partial toning with KRST is no longer considered satisfactory for image protection.

For adequate fixing film or paper should be fixed in two sequential baths. RC paper does not need to be treated with wash aid before washing. A 4 minute wash in running water is sufficient for long image life or for toning without staining. Fixing baths should be tested periodically for concentration of dissolved silver. For fixers used for film this can be done by measuring the clearing time of wet film and comparing it to the clearing time of the same film in fresh fixer. The old rule of thumb is to replace the fixer when the clearing time doubles but this is probably too liberal for archival fixing except for the first bath of a two bath system.
Since paper clearing is hard to see its best to fix out a scrap of paper and check it with one of the residual silver tests. One can also use the Potassium Iodide test but its difficult to coordinate this with the amount of dissolved silver. The test consists of a solution of Potassium Iodide with a preservative of such strength that it will form a permanent cloud in fixer with more than a give amount of dissolved silver. All of the above tests are detailed in the Kodak publication _Black and White Darkroom Dataguide_ and elsewhere.
I will post them if they can not be found.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx 

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