Homebrew PCBs

On Sat, 6 Oct 2012 23:38:39 -0400, you wrote:

>I am doing some tests with dry film photoresist.  Can you guys recommend a
>bulb that can be used for a dark room light?  Are there any simple methods
>to using a regular fluorescent or incandescent light for the purpose?  Maybe
>covering the bulb with a color saran rap as a filter?
>
> 
>
>Jeff
>
Take a look at red or yellow fluorescent tubes with an inch or so
of the ends wrapped with black electrical tape (the coating may not
extend all the way to the end cap and thus leak UV). We did have 
to use standard start tubes; the rapid start used a different material 
and were not safe (at least the red ones, I didn't test yellow).

I used a 20" red in my darkroom for years. It was significantly
"safer" than the high dollar Kodak glass filters . 

Back in the '60s an area newspaper had offset presses and the 
room where they made the plates had yellow fluorescent. 
You could walk in there from the composing room and have no trouble
moving around.

You will need to check the current production. A good test is to lay a
piece of sensitized material face up in your working area and put
a quarter in the center. Leave it there for three or four times your
normal working time. Develop the material and if you can see the
outline of the quarter the light source isn't "safe".



Keith Bowers WB4LSJ- Thomasville, NC