I learned something new today and I thought I'd share. For all you folks who don't have a vacuum top exposure unit but who still want to print 65 lpi halftones, you can squeegee a thin layer of baby oil on the ink side of your films and smuck them onto your unexposed emulsion. It'll hold the film in place for as long as you need to run out into the backyard and let Mr. Sun shine his light on you. Makes great contact. Then you can degrease your film when you're done.
Here's what I did.
- baby oil
- Murakami Aquasol HV emulsion
- two yellow 200 mesh screens
- one commercially made 65 lpi 40% halftone contact screen
- one NuArc 5000W fliptop metal halide platemaker (in place of Mr. Sun.)
Okay, so that platemaker was the whole reason I needed to try something stupid like baby oiling my films onto my emulsion. The platemaker has this nice 5000w metal halide lamp on it. It's also got an integrator. And a vacuum bed. Only thing is since it's for making photopolymer plates the bed is only like a half inch deep. Won't hold a screen. So I needed some way to 1. hang my screens upside down in the unit while it exposes them (its a fliptop, light shoots up from below) and 2. maintain contact between my film and emulsion.
So I coated two screens, 1:2, and dried them for an hour with a fan.
Then I squeegeed a thin smear of baby oil on the printed side of my contact screen film. I smucked it onto screen #1 and smoothed it out. The film held on nicely, not sticky but firm. I put some black foam against the other side and cinch-strapped the whole setup onto the platemaker glass top. I flipped the top over and exposed for 5 different times (step test). I disassembled the rig and then washed out the screen with a power washer nozzle (the power washer wasn't on).
Weirdness. The dots in the 0.3 to 0.6 exposure unit range (around 45 seconds) made this crazy moire pattern. Here's a print I made. Excuse my hamfisted squeegeeing, nicked squeegee blade and the chunky black ink I found in the back of a cupboard.
The dots were kind of squarish. Not thorough enough washout.
I exposed screen #2 the same way. Oiled up the film, stuck it on the emulsion. Step test. Only this time I pressure washed (12" distance, maybe 1500 psi). 0.4 exposure units made some really nice shaped dots.
I don't know why some dots filled in. Bad technique? I made a bunch of prints and sometimes different dots would fill in, then clear up, then fill in again. The stencil had absolutely no blownout dots.
- sticking your film to your emulsion with baby oil works. Makes good contact and sharp stencil edges.
- power washing halftone stencils makes nicer shaped dots.