I have the opportunity to purchase a Thomas Duplex used at a reasonable price. It would be for my 6x12 darkroom (still under construction).

I've read the comments on wait time to reach steady brightness and that it may be too bright - at least with the doors open.

But is a lower watt bulb an option? As I understand, the standard Thomas-supplied bulb is 35w. I don't know if the Thomas bulb is proprietary (wouldn't think so but who knows). This site shows a number of sodium vapor bulbs with what I understand is the proper base, including an 18w:

Any experience with using a different bulb? Does anyone know the specific bulb type (including base) required? I have not been able to find a manual for the safelight online.