I use 1/2" rod and have no problem with maintaining paper contact and 1/2
inch rod over such short lengths (up to 22") doesn't bend, especially since
I make my handle out of 1/8" sheet acrylic and run it nearly the whole
length of the rod. Another responder said he had problems so who knows? (I
have not had the problem he did with sensitizer sticking to the rod; I
rinse mine after every use.) I've been using acrylic rod coaters for all my
Pt/Pd workshops over the last few years and they work well for everyone.
With large pieces of paer (11x14 and over) I will sometimes lift the paper
from one side and "push" the coater rod and sensitizer into it, uncurling
the paper as the coater moves across the paper. I would think the same
might be necessary with glass rods.