LPS lamps require a ballast. I don't know if the 18W lamp will operate properly off a 35W ballast, but it's something you should check into before buying, aside from other issues. Likely someone else here on APUG will know about the ballast issues.
I have a Thomas in my 10'x10' darkroom. It is in the middle, close the 8' ceiling.
I replaced the filter in the upper gates with a piece of cardboard painted flat black. The yellow filters are in the unit near the light. When I print silver gelatin, the gates are open about 1-1 1/2". When working with alt processes the gates are wide open.
I have used them in this manner for about 20 years and never had a fogging problem.
I have red filters in the gates. I use my Thomas with the gates completely closed in a 6x12 darkroom and it's still plenty bright...though not as blindingly bright as with the gates open. The light it produces is still yellow, not red.
I purchased that 18w bulb--it does work in the Thomas (no, the Thomas bulb does not have a proprietary base), and I'm still using it almost one year later. But I didn't notice much difference on the light output. It was still too bright without cardboard shields covering about half the opening.
Originally Posted by mgb74
One would think that, with half the wattage, there would be a noticeable reduction in light. But at least the bulb is less expensive than the "correct" one from Thomas.
Originally Posted by resummerfield
Thanks for the info.
I installed a Thomas safelight in my darkroom about a year and a half ago and can't live without it. I've never had any problems with paper fogging with graded or VC paper. I use mainly FB paper. I also leave it fairly open and my darkroom is about 12X18 feet, and not entirely light tight. The problem I seem to have now is the thing is making noise as though the ballast is going bad. Has anyone had any experience with noisy safelights or bad ballast? If it is a sign of the bulb going, I'm curios about other folks experience with alternative sources for bulbs. The Thomas safelight was manufactured here in Charlottesville Virginia, and the word is that the Thomas family is no longer in the business of making or selling replacement parts. For those who love their safelights, I would suggest picking up a back up or at least stocking up on a spare bulb as they will not always be around.
The bulbs are all over the place, look for a 35watt low pressure sodium bulb at like 1000bulbs.com or someplace of that ilk. They should be about $40.
I have one light that is starting to make noise, but I leave it on almost all the time. I've been running it for 10 years.
I actually have almost 8 of these things. People keep giving them to me. lol
thomas duplex safelight
How do you connect the end of the light to the net ? I can't use the electric small US pins on our European Electric net system .Do I need a transformer to let work the safelight or intermediair connectsystem to use the American pins on the Europe electric net .If I need a transformer ,where can I find it ?
Yes, you need a transformer to convert your 220 volts to the safelight's 110. If nothing else, check eBay for one.
Thanks for taking the time to do a test...
Originally Posted by jeroldharter
Well, there you have it. I thought the sodium vapor bulb was inherently safe...
Makes me wonder... Is your problem faded filters? Is it the extended spectral sensitivity of your VC paper (where maybe the Thomas would work great with Graded papers)?