In the '80s, I used bulbs that fit that description to expose negative resist coated boards.
They were called "Gro" lights. There are several brands, that was the one I used. Just a 65W reflector bulb about 18 inches away, clamped under a sheet of glass very close to what you describe below.
I think it took about a minute and a half?
Steve Greenfield AE7HD
--- In Homebrew_PCBs@yahoogroups.com, "Todd F. Carney / K7TFC" <k7tfc@...> wrote:
> Back in the 70s, I used to expose offset printing plates using a 300w blue
> frosted bulb with a high-UV output. It was just a regular screw-in
> (Edison-base) bulb and I used a common clamp-on lamp at about 30." I used a
> sheet of 1" sponge foam and a 1/4" thick glass plate to clamp the negative
> and plate during exposure. A very crude but also very effective setup. I
> just did a Google search for those bulbs and I haven't found them yet. I'll
> keep looking.
>
> 73,
>
> Todd
> ------------------------------------------------------------------------------------
> K7TFC / Medford, Oregon, USA / CN82ni / UTC-8
> ------------------------------------------------------------------------------------
> QRP (CW & SSB) / EmComm / SOTA / Homebrew / Design
>