I've been working with the one-exposure "halftone" method of exposing ImagOn plates, but I'm also experimenting with the two-exposure method, which includes exposing your plates with an aquatint screen.

I was doing a test to get correct aquatint screen exposure time, exposing the plate with the aquatint screen in 5 second intervals, from about a 15-second to a 60-second exposure. My understanding is that I should look for an exposure that gives me a rich black print tone.

I printed the plate, and I get a rich black ink tone starting at about 20 seconds, and going up to 60 seconds. I will next do a step test with my image transparency to get the correct time for that exposure.

My question is, since there such a range of "correct" exposure times for the aquatint screen, is it better to do a longer exposure or shorter one? I read somewhere that a longer exposure is better (assuming your getting good results) because it hardens the plate. (I've noticed that sometimes ImagOn plates feel a bit sticky when I start to work with them, and I was assuming this was from short exposure times?)

I was thinking that I might use about 30-40 seconds, which is not at bottom end of range, but not that long either.

My second question is, what happens if I continued to test with longer exposures of the aquatint screen, say up to two or three minutes? Is there a certain point where the exposure is too much and you lose tone? Many of the people in my print studio use up to 3 minute aquatint exposures, but they are using a different developer than I am, and this seems a bit long to me.

Best, David.