i was wondering, if it makes sense to replace the hypo clrearing agent bath with something closer to sea ater, not eliminating the sodium sulfite (2%)but adding actual sea salt(3.5%)and maybe somemagnesium chloride(0.25%)just a thought, for dis cussion.
Kodak did extensive tests with various salts and found out that sodiun sulfite was the most effective. IIRC, Agfa tried sodium chloride for a short while then sodium carbonate and finally sodium sulfite.
Kodak did extensive tests with various salts and found out that sodiun sulfite was the most effective. IIRC, Agfa tried sodium chloride for a short while then sodium carbonate and finally sodium sulfite.
You are right I should have checked my notes before mentioning Agfa but I was in a hurry and didn't want to dig them out.
However from my freshly dug out notes --
Agfa recommended a 2% solution of anhydrous sodium carbonate. For single and double weight papers, wash the prints for 10 minutes. Then soak the prints for 10 minutes in the working solution with frequent agitation. Finally, wash the prints for an additional 5 minutes. Useful capacity is 100 8x10 prints per gallon of working solution. In any case, the used working solution should be discarded after 24 hours.
i gather ,the recommendations was identical to sodium sulfite...2%, which is interestinglyvery closely matchingthe global average of sodium chlorideat about 3%.My question again would a combination of different salts work better than hca alone?
Somewhere on this sight I once saw a list of different salts (sodium sulfite, Sodium Carbonate etc.) and how effective they are in washing. Where on this site I do not remember.
It may have been Henk Rolfsa who suggested using 3% Sodium Carbonate and 1% sodium chloride (sea salt). However I am not sure about this.
Somewhere else I once read that a combination of different salts improve the washing performance of a wash aid.
Although the sodium chloride must be removed completly because the chloride may damage the photo over time.
I have read some posts, probably at rec.photo.darkroom before it went feral, by Richard Knoppow, citing Kodak research describing experiments that eventually showed that sodium sulphite was the best wash aid. As you know in Kodak HCA its pH is adjusted by moderately acidic metabisulphite.
Agfa used to recommend carbonate but I think the relatively high pH of it can be a disadvantage to the paper emulsion because it softens it. It also might be not at an optimum pH for best rinsing. Isn't there a pH (the pH of Kodak HCA) where the gelatin is in some optimum state for fastest washing?
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