[Alt-photo] Simple fix for clean borders on Pt Pd prints

[Denny]

I couldn't figure out why I was sometimes seeing some "dirt" in the white
borders around some platinum prints, looking almost like incomplete
clearing.  I tried changing clearing routines, more acidic coating solution,
more acidic developer, different papers, and nothing seemed to work.  Then I
filtered my Potassium Oxalate developer through a coffee filter, and that
solved the problem.  I'm printing with sparkling white borders again.  I
normally replenish my developer, but the sludge at the bottom of the bottle
was the culprit.

Happy New Year!
Denny