Screen %age difference


Well-known member
Hi All,

We are using Screen CTP machine. Recently we found difference in screen %ages
Ex. I tried with Black 50% screen for whole plate, after checking I found 48%, 45%, 43%, and 47% in different sides.

I checked with screen %ages from 2 to 100 for 4 sides, found same problem, all 4 sides are reading different screen %age. Can any one guide me why this happens and how to control the same
We are using Thermo star CTP Plates


Well-known member
First thing is to check your plate processor. Bring the processing conditions into control especially paying attention to the developer brush, dev section, circulation pump(s), check all rollers ok and adjust them if necessary, clean the machine again if needed. Will probably take you one day work. When you're happy with the result redo the 50 percent uniformity test twice, first time let it run into the plate processor straight, second time turn it 90 degrees by hand and feed it for processing. See what happens, compare the two tests. Do you notice bands/streaks or is it just percentage variation ?


Well-known member
First of all so big difference in the percentage is very very unusual. Please after check of the processor conditions (as maxon said), see if there is any difference in the size of the dots. They should be perfectly square, not a rectangle. If you have variation in the form, there is something with the PT-R. Try with another plates, or another batch. It could be from the plates.


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