Thanks, this may be a part of the possible answer.
That most important concern is will the acid also attack the gypsum
binder (calcium sulfate ? ) in the investment ( phosphate binder for
platinum investment)? Of course there is the issue of fumes and
burnout. Thank you Teri.
Just think, I could have told my student,"You are nuts, just do as I
say, go away don't bother me." The correct answer is important, so is
the thrill of the hunt!