[pure-silver] Re: Purple-Tinted Negs


----- Original Message ----- From: "Adrienne Moumin" <photowonder2010@xxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Wednesday, May 31, 2006 1:42 PM
Subject: [pure-silver] Re: Purple-Tinted Negs


Belated & heartfelt thanks to all who took the time to respond, it took me a bit to bounce back after all the holiday weekend schlepping!

From her comments, I think my friend is using both TMax and Tri-X. I think after all of everyone's help she shouldn't have the problem again!

As is often the case in life as well as photography, an answer begets another question in reference to this excerpt:

The old rule of thumb still holds, measure the clearing
time and fix for double this time. The old rule is also that
the fixer should be discarded when clearing time doubles.
This might be OK for a two bath system but IMO is well
beyond the safe limit for a single bath.

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


How does one know when the clearing time should be increased?

Thanks,
Adrienne Moumin

By fixing out a scrap of film occasionally. Use a scrap of the film you originally tested with. Soak it in plain water for 2 or 3 minutes (longer is OK) and then fix it and watch to see when the cloudiness disappears. The reason for soaking in water is that the rate of fixing for wet film is different from dry film. Since the film is wet in practice it should be wet when testing.

Its important to understand that clearing is not the same as fixing. The film can be visually clear and still have enough halide left in it to cause trouble later. However, the time it takes to clear is a good indication of the amount of silver dissolved in the hypo.

Another test is to use a solution of Potassium Iodide. When this is added to fixer it combines with the silver to form Silver Iodide in the form of a cream colored cloud. The amount of dissolved silver which results in a cloud which is not immedediately dissipated depends on the dilution of the test solution. Kodak gives instructions for testing both single and double baths but I think there is an error in the instructions for the two bath system. I have not been able to substantiate this. In any case, its easy to see when film clears and its a more direct test.

The degree of fixing can also be tested using a solution of either Sodium sulfide or Kodak Rapid Selenium Toner, diluted 1:9. The Sulfide test is standard. KRST can be used provided the film or paper is well washed because it fails if there is a lot of residual hypo.
A drop or two of the test solution is placed on a clear area of the film or paper and allowed to stand for about 2 minutes. It is then rinsed off. There should be no residual stain. Both Sulfide and Selenium will "tone" silver halide or incomplete fixer reaction products as readily as metallic silver so any stain will indicate the presence of silver in some form. Since this method tests the actual performance of the fixer it is probably the best test. When this test is used on paper I suggest using a scrap that has been processed along with the prints. The reason is that prints or film that has been tested should be washed following the test, which is, of course, not necessary when a scrap is used. Also, the stain, if it develops, is permanent. The film or paper can be re-fixed in fresh fixer but refixing will not remove the stain.
This residual silver test should be run on a routine basis where permanence is of concern. Also, it will show up prints that will give problems when toned ahead of time.

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

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