From: John Larkin
Subject: Re: homemade uv exosure unit
Date: Mon, 23 Dec 2002 19:34:18 -0800
Organization: Posted via Supernews, http://www.supernews.com
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On Tue, 24 Dec 2002 03:23:05 +0800, "Lord_Inex"
>> A 175 or 250-watt warehouse-type mercury vapor lamp is a great source.
>> A couple of feet away, it casts very sharp shadows and gives good
>> resolution. Up-close fluoresecent-tube or other area-type sources make
>> blurry shadows, different on the x and y axes.
>please dun get me wrong but have u tried the mercury vapor lamp that u
>suggested. i'm just curious and also im evaluating and collecting as many
>ways to do this as possible.
>apologies if i sounded rude.
Not rude at all. Yes, I used to use a mercury-vapor lamp. I bought a
175-watt unit that came with a ballast and a big reflector. I took off
the reflector and mounted the fixture horizontally, maybe 18" above a
workbench, and wrapped the top half of the bulb with aluminum foil.
This resulted in a pretty small, bright source that cast nice sharp
shadows, much sharper than using a light box.
I tried breaking away the outer glass envelope, which has a
UV-to-visible phosphor coating. That was supposed to expose the really
small, bright UV bulb inside, but I managed to break the inner stuff
too, so gave up on that. But just the way it comes, it gave very good
results with spray-on KPR negative resist, with maybe 5 minute
Nowadays I buy boards from AP circuits and keep from staining my
fingernails with FeCl.