Brumberger 5x7 contact printer question

I was just given a 5x7 Brumberger contact printer.

Inside there are three incandescent lamp sockets and a sheet of (flashed?) opal glass.

I looked online and found a picture of one with a frosted lamp, a clear lamp, and a red lamp.

The red lamp I understand...to get things set up, adjusting the easel blades etc.

Was there some purpose to using a clear vs a frosted lamp, considering it has an opal diffuser? Or maybe the clear lamp happened to be smaller, for different exposure times? It doesn't appear to have a switch to chose which lamp lights...it looks like it has one momentary switch to turn it on with pressure on top.

Thanks

One thing to check is how powerful the thing is. IIRC most [all?] contact printers were aimed at contact paper. Enlarging paper will be too fast.

OK, maybe I put a Black Light CFL in it & use it for alt-process.

Or the smallest lamp I can find for reg. paper.

Murray,
Plug it in to a light dimmer and it will probably work well.

I had a passing thought about that but it got knocked over by another thought.

I have a Variac that should work.

Murray

Or try a motor speed controller instead of a variac; these chop the duty cycle, rather than the peak voltage, so the color temperature of the lamp won't red shift as badly.

~Joe