that. We get the vac rubber from a wetsuit manufacturer for ours.
we just bought a raner unit for the school, that's all they use on the top - not a vucuum pump, a vacuum. It works fine.
A little tip on the lamps....if you want super fast exposures, consider using super actinic lamps from a tropical fish/aquarium supply. We use this bulb on our TMI Eagle Table top units - typically 90 second burns. On this Raner (with regular blacklight tubes) the time is 6 minutes on yellow.
$5 used canister vacuum will work. Must have a tight blanket for good suction
4mil plastic will work if you use a good quality half dome shaped weather proofing that goes around doors to place around the edge of your blanket frame.
I have used a 1/4" glass with a gallon of ink as weight to expose. what you want is a tight connection between the emulsion on your film and the emulsion on your screen.
Be sure your last coating of emulsion is pushed to the back of the screen.
Lights I have are two 500W quarts and two 18" blacklights.
I put the blacklights on a different switch to use when setting up the positve. I then pull down my blanket frame, lock into place turn on the vacuum and then the 500 watters. Be sure you have a small curtain cord attached to the vacuum opening. This must be long enough to cross over the length of the screen to draw the air out to creat the vacuum.
I used pond liner from Home Depot for a couple of unfiltered blacklight multitube exposure units I built. It doesn't have the stretch that wetsuit material has, so you have to leave some sag in it, but it'll pull down tight enough to get excellent exposures. Wood frame out of 2x2 wood, secured the rubber with some 1" x 1/16" aluminum strips drilled out about every 2" for some screws. Soft half-round door weatherstripping on the side that sits on the glass, and drilled a hole in the side of the frame to accommodate a snoot from a small shop vac. Couple it up with an old darkroom timer and you don't even have to babysit it. http://i174.photobucket.com/albums/w...ameoutside.jpg http://i174.photobucket.com/albums/w...raLabTimer.jpg
I built a huge one and bought a sheet of 3mil neoprene and it works awesome. Just make sure it's got nylon laminated on one side ( like most wetsuit materials). I made the mistake at first of getting raw neoprene and it just ripped right away. I got the valve stems at patchboy.com and just used some left over beerline tubing from my brewing supplies. I got the neoprene at Foam Mattress Pads Memory Foam Platform Beds & More but it was a bit more expensive (and thicker) than the replacement blankest they sell at ryonet Neoprene Vacuum Replacement Blanket 3mm Black 51x83".
I got this vacuum pump off ebay brand new for$148- and after almost electrocuting myself trying to wire it up- it works perfectly. I can pull a complete vacuum on a 50" x 60" area in about 20 seconds. With the vacuum pump you can regulate the pressure with a dial. I'm sure you could rig it up with a regular vacuum and make it work.
Do like Andy says and use the Phillips 40 watt 48" T12 Medium Bi-Pin (G13) Base Actinic Black Light Fluorescent Philips Light Bulb. My exposures since I switched to these bulbs is down to 70 to 90 seconds.
Thank you for the tips! I moved to a new studio last month and am just starting to build everything from scratch. We'll be building a vac topped exposure unit, washout booth, printing tables and a light tight box for screen storage. The drying rack I bought used.