Spray treating OHP for use with KM73 plates
I tested about 6 different spray products to try and come up with a good alternative to using baby powder with Pictorico OHP and the KM73 Printtight plates to mitigate air pockets and light patches in the image when using a vacuum frame. Thanks very much Susan Voss for the idea!
What I found was 2 light passes with Krylon Crystal Clear Acrylic Coating 1303 (it's glossy and perm) on Pictorico OHP (normal, not Ultra which I haven't tested) provides enough texture to avoid having to use baby powder. It adds just about 1% density on average to the Pictorico compared with 4% or more from other products and doesn't seem to introduce any noticeable mottling to the final print. Just make sure there's no dust on the positive before you treat it, and allow it to dry in a dust-free area, or whatever lands on it will be stuck to it forever, of course.
I also tried Krylon Crystal Clear Matte, Rustoleum satin clear finish, Krylon Workable Fixatif, and a Shuregarde product just for kicks (UV inhibiting lacquer -- duh). Didn't try any hairspray products, though that could be something to try too (thanks Jan).
Hope that helps. If anyone else decides to try the Krylon Crystal Clear 1303, or has better results with something else, be sure to post it.