Quote Originally Posted by Brook View Post
Fresh mixed ABC has almost no visible stain if used with an acid fix and stop. PMK has tons of general stain if an alkaline fix and water stop are used as often is done.
ABC would be a pretty grainy developer to use for enlargments, unless you like that look.
I have found that PMK used in an inversion tank does not produce much general stain. I don't have a lot of air in the tank, and I don't agitate a lot.

The OP needs more general info at this stage, I think. The articles by Sandy King at unblinking eye are a good place to start.

Introduction to Pyro Staining Developers

http://www.unblinkingeye.com/Articles/articles.html

If the OP is going to use variable contrast papers, the effect of stain colour on achieved contrast needs to be studied.