SamuliSchielke
Dear forum,
I’m in Cairo making prints for an exhibition (there’s a good rental darkroom here that I’d recommend: Contemporary Image Collective, 20 Safiya Zaghlul St. info@ciccairo.com), and this morning I realised I’d run out of fixer. The Kodak concentrate I wanted to use has turned milky white, and I take that as a sign that something is wrong with it. The only supplier here who sells B&W chemicals in quantities under 50 litres is waiting for a delivery from Kodak, which is due to arrive sometime in the next two weeks. So I’ve resorted to the sodium thiosulphate, which fortunately was in stock here in the lab. Not acidic fixing salt, then, but hypo in its pure form. I think I’ve heard that pure sodium thiosulphate solution doesn’t keep well, but that’s not a problem as I’m making my prints today and won’t need the stuff tomorrow (and in two weeks’ time, Kodak’s rapid fixer will be back in stock). The question now is, does anyone know if pure sodium thiosulphate has any other drawbacks compared to a fixer like A 300? Is there anything I need to bear in mind that I’ve overlooked?
The processing is as follows:
Paper: Fomabrom
Developer: Kodak Polymax
Stop bath: plenty of running water
Fixer: 15% sodium thiosulphate solution, 10 minutes
Water, Sistan
Many thanks in advance for your advice!
Regards,
Samuli
Wolfgg
Hello Samuli,
If you use pure sodium thiosulphate, the pH may be too low, causing sulphur to precipitate and resulting in this cloudiness. That is why Kodak’s F-24 formula is as follows:
500ml water at 50°C
240g sodium thiosulphate
10g anhydrous sodium sulphite
25g sodium disulphite
Top up to 1000ml
Regards, Wolfgang
SamuliSchielke
Thanks! The cloudiness was actually in the rapid fixer concentrate, not in the hypo. Due to time constraints, I’ll have to make do with pure thiosulphate today; before that, I’ll add an acidic stop bath. But all the ingredients for the recipe mentioned above are available here from specialist chemical suppliers, so next time I can mix up an acidic fixer myself if Kodak hasn’t delivered by then.
Regards,
Samuli
SamuliSchielke
Dear Forum,
Fixing with hypo worked well, though an acid stop bath is required beforehand. However, the paper mustn’t be left in the hypo for too long – for the first time, I saw with my own eyes how fixing for too long actually bleaches the highlights. Fortunately, it gave the print a nice effect, so it was a blessing in disguise.
But that leads me to another question: what are the ideal fixing times for pure hypo? The Darkroom Cookbook says 30 seconds, but that seems very short to me. For acid-based hypo fixers, however, the instructions usually specify fixing times of up to 10 minutes for baryta paper. Any experience with this? Can pure hypo be used for film?
If anyone is in Cairo over the next three months, the prints are on display here:
el-Nahda culture association, 15 El-Mahrani St, Al-Fagala, behind the Jesuit School.
Best regards,
Samuli
cfb_de
Hello Samuli,
The answer to your question is directly related to the dilution of the fixer. And no, there haven’t been any standard values since Hofrat Eder’s book.
Best regards,
Franz
