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  1. #1

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    Help, Thomas Duplex Safelight

    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?
    RJ

  2. #2
    Greg Davis's Avatar
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    Get new filters. There should be a set in the base above the bulb to filter the light for VC B&W paper and a set in the vanes. The two sets are not the same kind, nor are they the same size. The top filters are chosen for the kind of material used, i.e. color paper, ortho, etc. Most people use the ortho filters for B&W in order to control the intensity of the light, though black cardboard could be used in the vanes as well.
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  3. #3
    Ektagraphic's Avatar
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    I would get new filters if you still can. They don't make this safelight anymore.
    Helping to save analog photography one exposure at a time

  4. #4

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    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.
    Last edited by Richard Jepsen; 10-18-2009 at 09:02 PM. Click to view previous post history.
    RJ

  5. #5
    David A. Goldfarb's Avatar
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    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.
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  6. #6
    Greg Davis's Avatar
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    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.
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  7. #7

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    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.

  8. #8

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    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

  9. #9

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    "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.
    RJ

  10. #10

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    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.
    Last edited by Richard Jepsen; 10-19-2009 at 03:18 PM. Click to view previous post history.
    RJ

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