Re: spots and dots and UVBL solarplates
Christina Z. Anderson wrote:
Good morning all,Hey Chris,
I think it was several years ago I asked about it on the list and Jan was the main one who responded to me and ID'd the newton rings (maybe a couple others too). Since that time I've been on a long path away from the standard approach, solving problems, introducing others, solving them again, bit by bit until coming up with the procedure I published on-line last year. Jan was onto the right solutions too when he advised I dry the OHP with a hair drier and using baby powder. I just wasn't drying it long enough. Don't feel bad about blowing plates. I share that burden and have easily "wasted" a couple grand on materials in the past 3 years testing and tweaking...which is why I published my notes and workflow which at least a few people are following as a starting point. Plates are recyclable at places that accept scrap metal. :-)
Most industries now print direct to plate avoiding the transparency step entirely.
I've never ID'd why UVBL is a problem precisely, and stopped worrying about it once I got my Olec, but do know that a diffuse light source causes weaker shadows (take, for example, florescent lights in a classroom). Compare that to the shadow created by a point-source halogen lamp or even incandescent light. During screen exposure, this light-source, and shadow created from it, affects the shape and sharpness of the aquatint dots. Weaker fuzzier dots are still dots, but I believe create, on a very subtle level a slightly weaker, fuzzier, print. Since most point sources also come with a vacuum frame, this solves many of the dark spots and patch issues relating to poor contact which, according to Dan Welden and others, is the single most prevalent problem people have with this process.
Especially with larger plates (16x20"), the problems with UVBL becomes notably worse. I have a colleague who use tubes (tanning bulbs, I think) but only for small plates. Large ones were so problematic under UV tubes they use the sun now for those.
I think an easy test would be for you to try the sun...or borrow a friend or colleague's exposure unit to see the difference.
Been exchanging Email with a guy at Pictorico who said they're in the process of developing a matte OHP product which may solve all these problems (though maybe not the newton rings on the bottom of the glass (kreene > glass)). The solution of taping double-sided frosted mylar to the bottom of the glass sounded like a good one. Has anyone doing poly plates tried that yet?