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...


Quote Originally Posted by Kerik View Post

I agree we are approaching the infinite and useless level of discussion, but I have one last shot from my end. Muriatic acid from the hardware store is usually about 37% dilution. I don't consider that dilute and I don't want it in my darkroom. I speak from experience that it is more hazardous to use and store than oxalic acid. Being a liquid, HCl is all to easy to spill and the airborne vapors from an HCl spill dwarf the hazard from oxalic acid powder in my opinion.

You said: "I don't like the idea of "if the best do it, it's OK for me too" kind line of thought,"

Ummmm, me either!! Did I say I was "the best" or do things the way "the best" do? I'm just passing on my experiences having printed pt/pd for nearly 20 years now.

I haven't coated pt/pd with a glass rod since I found the Richeson 9010 brushes many years ago.

I'm not taking this personally and I appreciate your kind words about my work. Like you, I am just presenting my thoughts on the "right" way to do this.