Hi.. I have another question regarding exposure unit lamps. I know you guys get a lot these but I cannot find answers to this question... I am thinking about using a lamp for hydroponics, specifically a metal halide from Sunmaster at 1000 watts and 7200K. Would I be correct in thinking the colour temerature is directly related to the amount of UV A light produced ie. the higher the colour temperature the bluer the light and the greater the amount of UV A.
Any thoughts would be most welcome. Thank you.
Regards
Paul
I use hydroponic metal halide lamps for exposing as well. When I went down t the local grow shop and looked at the specifications they had for all their lamps, 7200K was the lamp they offered that output the most UV-A energy.
I use hydroponic metal halide lamps for exposing as well. When I went down t the local grow shop and looked at the specifications they had for all their lamps, 7200K was the lamp they offered that output the most UV-A energy.
Thanks Paul... was it a 1000watts and have you burned any fine halftones with it, is it any good, and what exposure times are you getting?
Regards
Paul
Although I told you that a 7200k light would work the best, all we have right now is a 5000k light. That was all the store had, and I've been meaning to go back and buy some 7200ks for backup and replacement - I just wanted to make sure the unit would work before I bought them.
I use ulano QX-1 emulsion. I use it because it was a fast-exposing emulsion and before this i had a fluorescent unit. I should probably switch.
Anyhoo, with the QX-1, double coated (wet on wet) from about 35-40" with a 5000k light, I expose for 2:15. The finest halftones I have burned are 55lpi, which is getting towards as fine as you would want to go, from what I understand.
The only way I'm able to burn those is that I have a vacuum sealing top as well. Fairly easy to build.
The only way I'm able to burn those is that I have a vacuum sealing top as well. Fairly easy to build.
Thanks for that Paul, that's just what I needed to know. I am knew to screenprinting and this sort of help is priceless. Do you think that the vacuum top is that much better than other options such as a compression lid. If so how did you make yours? Thanks again, I really appreciate the help.
Regards
Paul
I bought a sheet of neoprene (rubber) from my local screening supply store. You can get them on ebay.
I then made a square frame out of 2x3s that was the same as the perimeter of the top of my unit.
I tacked the rubber onto the frame with some pieces of wood and screws, and on the inside applied a bead of sealant so that no air can get out. I also put some weatherstripping on the bottom of the frame so that it seals with the glass.
I hinged the frame on the unit and put some clamps on to tighten it down. I bought the cheapest shop vac I could and what is called a universal tool adapter. It basically incrementally reduces the diameter of the shop vac tube so that you can attach it to other tools.
I bought a barbed hose connector and jammed it in the appropriate stop in the tool adapter, and on the other end i connected a garden hose, which runs through a hole in the frame to the inside of the vacuum top. Once the top is clamped down and you turn on the shop vac, is seals a frame really well!
Thanks again Paul... Just another quick question if you don't mind. What sort of thickness is the neoprene? I imagine this would affect the ability of the shop vac to pull the sheet into contact with the screen / glass.
Regards
Paul
The spectrum that is good for plants is good for us, preferable actually. It's the bluish looking light often seen in coral reef aquariums. The biggest problem you'll need to overcome is some sort of shutter, as your exposure times will be very short. (with pure photopolymer emulsion) Also, the lamps do not reach full power for at least 15-20 seconds, so just turning it on to start the exposure is not preferable.
A vacuum lid is indispensable in my opinion. Neoprene is the be$t, butyl and natural rubbers work well also. Look at pond liners.
I too wondered about the effects of the thickness of the rubber. The truth is, if you are using an actual vacuum pump, not a shop-vac, it doesn't matter what thickness you use. 20 inches of vacuum is 20 inches. Get a good vacuum pump, and use between 1/32 and 1/8 thick material.
5'x5' for $21 and some change. Free shipping. It's what I'm using now and I love it. Easy to work with.
Look on the Firestone web page too, they have a dealer locater on there somewhere if you need it now.
Give youself plenty of wiggle room. At least 3-4 inches on all sides, preferably more.
I too converted an old Nuarc platemaker into a vacuum frame. Now I use a converted window. Be sure hat you are drawing vacuum AT the screen or using a bleed cord, otherwise you can end up with a localized vacuum problem.
Colour Temperature of exposure lamp 
