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Exposure Units

Posted: Tue Feb 04, 2014 12:27 am
by S.TImmerman
I have two different exposure units and wonder if they can be used interchangeably - I hope this is not a stupid question


I have a standard Letralite Exposure Unit

and nice light box with a timer


I just got my 137 mesh screens for powder printing and am excited to try it!


Thank you very much!!!

Shereen

Re: Exposure Units

Posted: Tue Feb 04, 2014 9:37 am
by Brad Walker
If you have a standard Letralite it has a UV bulb, which is a different type of bulb than most light boxes. Each bulb would be specific to exposing a different kind of material.

Re: Exposure Units

Posted: Tue Feb 04, 2014 4:55 pm
by S.TImmerman
My light box doesn't have any lights yet.. i thought I was supposed to buy UV lights for that/ GLAD i asked- what types got in the Light box? I thought they were black UV lights? No?>

I'm confused now -ty for the help

Re: Exposure Units

Posted: Tue Feb 04, 2014 5:07 pm
by Brad Walker
S.TImmerman wrote:My light box doesn't have any lights yet.. i thought I was supposed to buy UV lights for that/ GLAD i asked- what types got in the Light box? I thought they were black UV lights? No?


A light box can have any kind of bulb, depending on how you want to use it, so you can certainly buy a black UV light for the light box.

The Letralite has a 15 or 25 watt black fluorescent light UV bulb. I'm not sure what wattage you'd want for your light box, you'll probably need to do some testing to find the right exposure time -- it will depend on both the wattage and the distance from the bulb to the item to be exposed.

Also, you need to make sure there's no leakage (i.e., light getting into the exposure area of your light box). If outside light gets in during the exposure, it will mess it up.

Re: Exposure Units

Posted: Tue Feb 04, 2014 5:09 pm
by Rick Wilton
Yes, you want uv bulbs for exposing screen printing emulsions as well as photomask in the letralite. There are different types of uv bulbs available there are BLB and BL, the BLB are the "purple" black light uv bulbs, your letralite came with a BL which is a uv bulb but doesn't have the filter that stops the visible light. So a BL bulb will illuminate a room AND have uv and the BLB doesn't illuminate the room. You can use either for photomasking but I think the bl helps with the crosslinking of the emulsion.

Not to mention potentially different wave lengths of light.

Re: Exposure Units

Posted: Wed Feb 05, 2014 5:42 am
by S.TImmerman
Thank you very much, I'll buy the right bulbs I really appreciate all the advice!

Shereen