AFAIK, concentration muriatic acid from hardware stores is something around 30-32%. 37% is "concentrated/saturated" HCl solution. In any case, both will fume. But there are enough diluted HCl products around -> calcium remover, toilet bowl cleaner and such (usually around 10%). I'm talking about these kinds of products not concentrated/fuming HCl... I totally agree with you about concentrated HCl. Why you insist that I'm suggesting concentrated whereas I clearly stated "diluted/non-fuming" before, I don't understand.
Anyway, acetic acid (or white vinegar) also can be used. (As I also said before...) Enigmatically, I had no comments about acetic acid but only about concentrated HCl - which I haven't suggested at all...
Could be that the practical consequences of using oxalic or HCl/acetic seems to be the same (which wasn't the case for me) but I still think diluted HCl or acetic acid is the way.
Oxalic acid will definitely leave neutralization products in the paper which may or may not affect results in the short term. (On the contrary I remember someone talking about the different results they were getting depending on oxalic acid strength; colder/warmer results when everything is the same in the rest of the process...) In any case, with pt/pd printing it's better to have a purer surface (= a surface with no alien content) to print on - instead of having paper that incorporates useless neutralization remains "which we know nothing about their future influence on the print's health". And that's a very good point to me since someone doing pt/pd is surely interested / concerned about the future of their prints...
Originally Posted by Kerik