More Research with Positive Plates

It has become a challenge for me to come up with a simple process to make positive plates that would keep as fine detail that commercial plates give. While this is now possible using the new technique with the fine tints, where particles of toner are placed far apart, it is the heavy inked areas now giving me problems. When it comes time to washout the exposed plate, the tiny islands of silicone on top of the screen emulsion are what is lost. The emulsion is not as well bonded to the plates or tough enough to hold on and gets brushed off during development. As I cannot get dual cure emulsion or re-expose the developed plates with success, I have been going back to using diazo powder as the UV sensitive base.

The problem here is to get a perfectly even film of diazo as any variation in density will show in the continuous tone areas. While ‘squeeze rolling’ is one of the better methods, the unit I built had untrue rollers bought from surplus and did not put on a good even film. Spreading the diazo with dampened sponge was worse, so now the project is to find a better system. By modifying the diazo mixture and using different application systems, I may be getting a bit closer to my objectives, but it is frustrating. This would not be as much of a problem if I used grained plates, which tend to hold a certain quantity of solution, but the smooth recycled plates show off any difference in application.

If I can succeed, I will use the easier screen emulsion for flats and diazo for halftones, with different colors added in. I still use other techniques like drawing directly on plates or transferring from Mylar, newsprint and now polyethylene.

Right now I will use up the stock of commercial positive plates for the halftone plates, but I want to use my own in the end. Actually doing research is fun if one is getting positive results.

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