From: Jeff Buck (jeffbuck@swcp.com)
Date: 12/13/02-06:30:28 PM Z
This is an addendum to the brief discussion the other day about the
possible use of ammonium thiosulfate "rapid" fix for alt, and is by way of
a cautionary note for those of us, and I think there are many, who fix our
film w/ ammonium-based fix... In the Film Developing Cookbook, Anchell
gives this very simple recipe for an ammonium rapid fix -- 800ml of 57%-60%
ammonium thiosulfate + 60g of sodium sulfite + 5g sodium metaborate and
water to make a liter = stock. Dilute 1:4 for working. Anchell says to
fix for three times clearing or 3-5 minutes. When the clearing time has
doubled w/ use of the fix, discard. I found much shorter clearing times,
1-2 minutes, applying the 3X test. I'd take a strip of exposed film, pop
it in the fix, and it would clear in 20" (fresh working solution). There
are warnings in Anchell and elsewhere, of course, re: over-fixing. I was
bugged by this discrepancy, however, and ran it by a couple real
experienced sheet film people who said, "Kick back; your numbers are right
on." I don't think so. At some point, a sheet film guy suggested that my
test strips might not be as "clear" as I think, and suggested this
procedure: Before popping the strip of exposed film in the tray of fix,
place a single drop of fix in the middle of the strip and leave it there
for way long, several minutes, while you do something else. Then take the
strip with the now real real clear "hole" in the middle and pop it in the
tray of fix. You will know the strip is REALLY clear when you can no
longer discern the "hole". With fresh fix, this takes about one
minute. Times 3 is the low end of Anchell's "3-5 minutes". -JB
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