After buying 500g of potassium persulfate and using 30g (in a reducing formula) I now find myself with 470g of the stuff. Anchell's "darkroom cookbook" (1st edition) lists the primary photographic use of pot. persulfate as a hypo eliminator, but he does not provide a formula. I understand that hypo eliminator needs to be used cautiously as it can prove harsh on the silver, but since I may have the primary ingredient lying around, I thought I might give it a try.

Does anyone have a formula for hypo eliminator (not hypo clearing agent) and/or comments on its wise use?

As an aside, I have a bottle of Berg Bath which describes itself as a "hypo eliminator", but I believe that it is actually an HCA. Can anyone confirm?

Thanks in advance,

-- Eric Pederson (epederso@darkwing.uoregon.edu), February 19, 2002

Answers

If you go back to 1938, Neblette wrote about using a 0.2% solution of caustic soda and potassium persulphate (no proportions specified) as a hypo eliminator. He was quoting A.E. Amor, BJP, 1925. Ancient info. Today's wisdom is that hypo eliminators are to be avoided. Kodak's HE- 1 (ammonia & peroxide, I think) is now recommended for cleaning work surfaces of fixer contamination, but not for prints or film!

-- Conrad Hoffman (choffman@rpa.net), February 19, 2002.