Quote Originally Posted by sanking

1. Michael proposes using a weaker solution of potassium oxalate because this apparently gives better clearing in his condition. I am assuming he mixes the PO solution from well water rather than with distilled water?
No, I am suggesting only that a lower concentration of developer will probably clear out of the paper to minimal levels faster, which could reduce the possiblity for the oxalate to accumulate as calcium oxalate, if that is actually what is happening.

Generally you need no higher than about a 25% solution to develop well, so a 33% solution is a bit more concentrated than is necessary to do the job. No sense loading more oxalates into the paper fibers than is necessary to do the job, especially if there is a problem with calcium in the water.

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Clay mentions that he uses very high temperatures without problem, and I have also used the developer up to about 160-170 without this problem, but I don't do that on a regular basis.

What does happen with the developer this hot is that it blows out the sizing in the paper rapidly. If this happens, the PO and other chemicals can penetrate deep into the paper and it will take considerable effort to get them completely out in the wash cycles.