----- Original Message ----- From: "Bogdan Karasek" <bkarasek@xxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx> Sent: Thursday, December 03, 2009 3:02 PM Subject: [pure-silver] Problem with 2 tray hypo (fixer).
Hello, I need some advice/clarification regarding my fixer. When printing fiber paper, I use the two tray method for my fixer and I mix it myself using Sodium Thiosulfate in distilled water. When tray I is exhausted, I do the usual routine, move the hypo in tray II to tray I and mix a fresh gallon of hypo for tray II. Recently, a phenomenon has happened for which I have no explanation. If I am doing intensive work over several days, I leave the the chemicals, Stop and Hypo (developer gets changed everyday) in their trays overnight but each tray is covered with Saran Wrap to prevent oxidation. Never had a problem until last week. Overnight, Hypo II changed colour to a light amber (see photo) whereas hypo I did not. I checked hypo II for exhaustion using Edwal's Hypochek and everything was clear. As a precautionary measure, I mixed fresh hypo for tray II, covered it with Saran Wrap at the end on the evening and next morning, tray II has the amber colour whereas tray I is clear. I checked tray II with the Hypochek and again, no evidence of exhaustion. Since an image is worth a 1000 words, what you see in the photo are the contents of tray I on the left, clear, and tray II on the right, amber coloured. By the way, the developer is Dektol 1:2 and the stop is Kodak Indicator Stop Bath. Nothing has changed in my procedure, same trays for the past number of years, always mix chemicals with distilled water. Anybody have an explanation? This has never happened to me before. http://s873.photobucket.com/albums/ab296/bkarasek/?action=view¤t=Hypo12-01.jpg Cheers, bogdan
I don't have an explanation but if you are using plain
hypo you should be adding some sodium sulfite to it to
preserve the thiosulfate. Where there is no acid about 5
grams per liter is enough although more won't hurt. Plan
hypo oxidizes pretty fast without the preservative.
If this happened only once I suspect something got
spilled into the tray.
Hypo-Check shows dissolved silver as a precipitate but
will not show other problems such as sulphurized hypo. I
have some question about its reliability since the dilution
is unknown so the threshold of showing the precipitate is
also unknown. Hypo can be checked indirectly by using a
residual silver test on a scrap of paper or film fixed in
it. The simplest test is a 1:9 dilution of Kodak Rapid
Selenium Toner. However, this fails if there is much hypo in
the material so it should be well washed before testing. The
standard test is a solution of sodium sulfide but the
Selenium toner works as well providing the material is
washed and the test solution does not smell and lasts longer
than the sulfide solution. The test is made in exactly the
same way as the sulfide test, place a drop of solution on
the emulsion in a clear area and allow it to sit for about
two minutes. Then rinse off and look for any staining.
Properly fixed film or paper should show no stain. If
there is silver halide present there will be a yellow or brown stain. The Kodak Hypo Estimator comparitor works for the Selenium test as well as the sulfide test but there really should be no stain at all. -- Richard Knoppow Los Angeles, CA, USA dickburk@xxxxxxxxxxxxx ============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.
