Help, Thomas Duplex Safelight

Richard Jepsen · Oct 18, 2009

Yesterday the community DR Thomas Duplex Safelight came crashing down from the ceiling to the floor. Glass on the vanes broke but still hold what looks to be a dark filter. The sodium bulb still works. I have rigged other safe lights until I determine what action to take. I teach in the DR so I would like to get back to higher light levels from a Thomas Duplex.

The question is if we should buy another safelight or use the damaged one. What is the purpose of the glass vanes. It looks like the sodium light was never really filtered but just reflected up and out the vanes. Do the vanes really require a filter?

Ektagraphic · Oct 18, 2009

I would get new filters if you still can. They don't make this safelight anymore.

Richard Jepsen · Oct 18, 2009

Folks, the vane filters are super thin. The glass is thick but broken. Most of the glass remains in the vane metal frames. I tossed some of the pieces of paper-thin filter. It was a very dark color. The vanes still hold most of the filter material but apparently there was no filter between the sodium vapor light and open doors. It would appear I could use the safelight again. The emitting light wavelength is the raw sodium vapor color which is similar to an OC filter.

I would not know just how to install filters and they cost around $50.

David A. Goldfarb · Oct 18, 2009

The filters and glass are a unit. They just slide in and out.

Given how cheap these things are used, though, you might just look for another one and keep one for parts.

mgb74 · Oct 19, 2009

A related question. I have a Thomas Duplex with glass that is cracked. No glass pieces missing and the embedded filter seems intact.

I was hoping to either tape over the glass (to prevent it from breaking further) or possibly even glue a piece of thin, clear acrylic on the glass. Does anyone know how hot the glass gets after a couple of hours with the vane closed? I suppose I could even use the metalized tape meant for heating ducts, but that would block light with the vane closed.

I know I can buy a new set of filters for $50, but don't what to do that until I see if the safelight gets too hot for my small darkroom.

Shadow Images · Oct 19, 2009

The filters can be made out of ruby and amber lith sandwiched between glass, tape together with gaffers tape. I have made quite a few sets for my and local LF'ers. It's fairly easy and supplies are available at local art supply houses

Richard Jepsen · Oct 19, 2009

"The light is fine without filters when using graded papers, but in my experience, VC papers fog quickly without the DUB filters in the base."

What is a DUB filter in the base and how are they installed? I did not notice a filter between the sodium light and the vanes.

Good info on how the filters are sandwiched between glass which slides into the vane frame. That should make it easy to replace if we decide on that course of action.

I printed with Varycon paper using the safelight before the incident. Varycon paper requires a red safelight. The vanes where closed 3/4 from wide open. The paper did not fog which makes me believe the sodium light without filters is ortho safe as long as its not too bright. Is this true?????

It was rotating the hanging safelight after using Varycon which resulted in the ceiling hook giving way. Is this not a robust piece of equipment for the bulb to survive a fall to the sink and then the floor.

Richard Jepsen · Oct 19, 2009

A google search answered some of my questions. DUB is related to the safelight name. I still have a question about how a filter would fit between the bulb and the glass vanes????? I'm thinking the only filter is laminated between the vanes.

The google search matched info on this thread.

The Thomas contains a single, exceedingly bright, sodium vapor bulb, which emits VERY STRONGLY on the 589nm sodium line pair, but almost not at all at any other wavelength. In theory, 589nm should be safe for any paper which is safe under OC safelights. In practice, this is more or less true. VC papers, which have extended sensitivity relative to graded papers, are a lot less safe under the Thomas than graded papers are.

There was also a paragraph that mentioned a 15 min warmup time before the light is safe.

I suspect I need to re-install the safelight and conduct paper tests. Our DR has black ceilings so the unit with near full open vanes projects up to the ceiling which sucks up the light. I did not experience fog using VC paper from Ilford, Oriental, Forte, & Arista Premium (FOMA re-branded). Maybe our light is lower wattage and therefore less bright.

Richard Jepsen · Oct 19, 2009

Thanks for all your replies. Thomas Instruments no longer manufactures the safelight. They still make and sell parts and are reached at 434-842-9475. It is likely in our community DR we avoid fog issues as the ceiling is panted black and sucks up excessive light. A yellow filter coded FBD fits into the body as Greg mentioned. The vanes/wings hold a red filter coded FOD.

Richard Jepsen · Oct 20, 2009

I am following up on this post for historical documentation. The Thomas Duplex is a super model with two prong plug. No filters where in the body or near the top opening into the body. Installed in one vane/wing was a blue crinkled filter sandwiched by glass and the other vane/wing a dark orange/red filter. In replacement I hung a Kodak 10x12 OA light with 75w compact florescent. Fomabrom Variant VC-FB fogged in 2 min. Ilford WT FB was fog free after 7 min. The damaged Thomas Duplex Super output did not fog Fomabrom. As hung the Thomas Duplex light output was dimmer but wider coverage since it reflected off a black ceiling to the walls.

I teach a darkroom class and a student material costs are a consideration. Excellent less expensive FB papers are orthochromatic. It looks like the best path is to replace the Thomas filters with the ortho filtration.

Richard Jepsen · Oct 20, 2009

Greg, thank you for following this post. You have added to my knowledge. I'm considering ordering FOD filters. Are body filters a different size then filters in the vanes/wings??

Would you recommend some other safelight?

Above each enlarging station are screw-in light fixtures. Jumbo red bulbs @ 25W are na option. I can replace the Kodak 10x12OC filter over the sink with a 1A. The OC's direct illumination is brighter than the Thomas Duplex reflected-light. That may hold true for a 1A filter.

Purchasing (6) jumbo red bulbs and 1A filter for the Kodak unit is the most expensive option. However, who knows how long the bulb will last in the Thomas; especially after a crash from the ceiling.

Phil · Oct 20, 2009

I found some SOX35 low pressure sodium vapor lamps online that appear to be the same (or very similar) as the original lamp that was in my safelight - work fine for me, but I use AZO/LODIMA. Price was about what Greg mentioned -(a bit less, IIRC) Life is listed as 18,000 hours for these lamps. The one that was in my safelight did have a sticker that said it was a special photo lamp. As always, YMMV...

Help, Thomas Duplex Safelight

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