PMK minimum hypo strength

[pasha]

I've been shooting mostly 4 x 5 tri-x, some 35, and developing in PMK. Hutching's book suggests avoiding acid stop and fix so I do. I use water stop and went to THE DARKROOM COOKBOOK for a fix recipe and use the TF-2 Alkaline Fixer. Per the author's recommendation I don't use the sodium sulfite in the mix which leaves sodium thiosulfate and sodium metaborate. This recipe is 25% hypo! that is, 250 grams hypo per 1 l. water.

Could I safely cut it back to, say, 10% and do a tail test? Or 15%?

It seems like an awful lot of hypo to throw away every time. Thanks.

[Doremus Scudder]

Pasha,

Use your fixer to capacity, then you won't be throwing away good fix! Anchell recommends 20 8x10s per liter for TF-2 (both film and paper, but don't use the same fix for both!). You can mix a smaller quantity for just a few negatives/prints, making sure you have enough solution to cover, or, you can add the sulfite (I don't think leaving it out has as large an effect on image stain as some people believe). That way, you could save the fix in a full, stoppered bottle for a week or so.

Alternatively, save up enough film to do a larger batch. Half a liter does 10 8x10 or 10 135-36 rolls, etc. 250ml does five. Saving up five rolls shouldn't be a problem.

There are some who use rapid fixers one-shot. I've experimented with this a bit, but find it too time consuming. If you wish to try (even with your standard fix), do a clip test beforehand and fix the film for three-times the clearing time. I wouldn't dilute more than, maybe, 1:3 with standard fixers. Even this may result in times unacceptably long.

Fixer is relatively cheap, and tossing it a bit early ensures that it is not exhausted. Maybe you are being overly economical...

Good luck,

Doremus Scudder

[pasha]

Thanks for the thoughtful response. I've been diluting the hypo a little bit and doing the clearing-time-test with good results. I'd like to save as much hypo as possible, that is, as little waste as possible, but finally, the point is to have properly prepared negs.

[D. Bryant]

I've been shooting mostly 4 x 5 tri-x, some 35, and developing in PMK. Hutching's book suggests avoiding acid stop and fix so I do. I use water stop and went to THE DARKROOM COOKBOOK for a fix recipe and use the TF-2 Alkaline Fixer. Per the author's recommendation I don't use the sodium sulfite in the mix which leaves sodium thiosulfate and sodium metaborate. This recipe is 25% hypo! that is, 250 grams hypo per 1 l. water.

Could I safely cut it back to, say, 10% and do a tail test? Or 15%?

It seems like an awful lot of hypo to throw away every time. Thanks.

Pasha,

Don't throw the fixer away, save it for future use. You can cover the container with plastic wrap and it will work fine right up to capicity, at least that has been my experience.

Don Bryant

[pasha]

Thanks. You're saying that the straight hypo (without preservative) will keep? That would be cool.

How would I test it before using it? With a couple drops of that stuff? Or, do a tail-test?

Thanks.

Pasha