Here's a cheap method to create a light table to burn the photo emulsion on your screens.
i made this table for 20x24 screens, so the final size is 27.5x26x9in. i used leftover wood from a rocking chair i made for my Girlfriend's b-day (see my other instructables). i used 3x 24in double fluorescent light fixtures, but you could easily make a bigger table with 4' fluorescent fixtures. you'll need wood for the box, fluorescent fixtures, a timer switch (or a regular on/off switch) and some aluminum tape (or glossy white paint).
Step 1: Build a Box
that's easy enough, 4 sides and a bottom. size can change depending on what screens you have or what fluorescent tubes you're going to use. i used a router to make a step on the top edge where the glass will sit. this needs to be as level as possible otherwise the glass will not sit flat. also make sure are your corners are at 90 degrees otherwise you're gonna have a hard time to fit the glass.
i taped the entire insides with aluminum tape to maximize the light. this tape is expensive but i had a roll leftover from the house build. you could use glossy white paint.
Step 2: Adding the Lights
Get rid of the plastic cover, or better yet keep it to make something else... then bend back or remove any metal that might prevent the light from going everywhere (see annotations on 2nd picture). i used 3x fixtures so i wired all of them together in a electrical box, then the wires go through the wooden box to another electrical box that houses the switch. i used a timer switch which has proven to be relatively precise, but you can use a regular switch and use your phone or a cooking timer. then leave at least 5ft of wire and add the plug.
i had a window and mirror place cut me a glass at the right size, also had them slightly bevel the edges so i dont lose any fingers. cost me about 40$ for a 0.25" x 26.5" x 24.75" piece of glass including the edges. you could get it tempered but its much more expensive. i made a little notch in the top edge of the table to be able to easily remove the glass.
Step 3: All Done!
You could add legs to the table, i decided not to do it and keep it on the desktop for now.
i used 4100k lights, but use whatever is closest to daylight. i think its the UV that burns the emulsion, not the lumens (dont quote me). all i know is i used this setup before with SpeedBall emulsion and it worked fine using a 10 minute exposure time. the exposure time will vary depending on the emulsion brand you're using, the amount of fluorescent tubes you have and the distance between the light source and the screen.
Since this table doesnt have a vacuum cover, its important for you to cover your screens with a blanket to be sure no light spills over the film, then add weight on top of it so the mesh is flat against the film, and the film is flat against the glass.
hope this helps!