Käro requested that I do a post on my exposure setup and times and whatnot, so here we go. The picture above is probably the best photo of my unit in action.
For the light source, I’m using two 500W halogen worklights. These should be available at any hardware store for $15 (US) or less. They usually look like the picture above, but I removed the cage and protective glass. It didn’t say on the box, but some glass has UV protection properties and you want all the UV you can get when exposing, so I took it off just in case. I also removed the normal metal base on the light. Then, I built a very simple frame using scrap pieces of 2 by 4s and 1 by 2s that I had around. The work light can then be screwed into the top bar of the wooden frames and angled accordingly. The bottom of the light’s reflector is about 24 inches above the ground. The lower your bulbs are, the quicker your exposure, in theory, but you’ll also get less light coverage over your whole screen.
In the top image, the screen is sitting on a 3 inch thick slab of foam that I cut to the inner dimensions of my screen. On top of that is some black paper (supposedly cancels out some light reflection that could mess with your exposure times), then the emulsion-coated screen, then my positive (I use inkjet transparencies, a little more expensive than I might like, but they work really well), and to top it all off, a piece of glass that I took out of a cheap picture frame. The glass sandwiches the positive and screen together between the foam, giving you a tighter seal, so you don’t get any light leakage under your positive.
OK, onto exposure times. First off, the emulsion I use is Ulano QTX. I started out using Speedball Diazo emulsion, the kind that comes in their kits, but I’ve moved on. With the setup above with two worklights at 24 inches off the ground, my exposure time is 17 minutes for a screen with yellow mesh, and 14 minutes for a screen with white mesh. I’m pretty sure that I could easily lower my light source at least another few inches and I’d be OK and get lower times, but for the time being, I’m too lazy to change it and I’m getting good results so I’m happy.
One last bit of advice, don’t take my setup or exposure times as law, figure out what’s going to work out best for your space and abilities. And as much as you want to, don’t just jump into exposing something for a print, DO A STEP TEST UNTIL YOU FIND YOUR OWN PROPER EXPOSURE TIME! If you don’t know what that is or how to do it, just ask and I can do a post about it later this coming week, OK?
