I <3 Thomas Duplex

Discussion in 'Darkroom Equipment' started by ParkerSmithPhoto, Jan 2, 2012.

  1. ParkerSmithPhoto

    ParkerSmithPhoto Subscriber

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    I bought a used $40 Thomas Duplex safelight today. The filters were kind of beat, so I replaced them with Rosco #19 "Fire" which has the right type of wavelength cut off:
    19.jpg

    The thing is so bright you just don't expect it to be safe, but it is: after flashing some MGFB IV and doing a ten minute coin test with the unit full open, there was not the slightest hint of fog. It's like daylight in the darkroom!

    EDIT: THAT ? WAS SUPPOSED TO BE A HEART
     
    Last edited by a moderator: Jan 2, 2012
  2. mdarnton

    mdarnton Member

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    The darkrooms where I've seen them, they've been closed down a bit to cut down the light. There's so much that it tends to get in the way.
     
  3. Newt_on_Swings

    Newt_on_Swings Member

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    Yea I love my Thomas Duplex, its hard to use anything else after using one. Makes things like reading variable contrast filter values off the pamphlets of papers very easy.

    Mine has developed a buzz, so I might have to change the sodium vapor tube in it soon.

    You got a great deal!
     
  4. RalphLambrecht

    RalphLambrecht Subscriber

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    i'm not a fan!
     
  5. ParkerSmithPhoto

    ParkerSmithPhoto Subscriber

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    Aw, c'mon, Ralph. What's not to love? It's bright and safe. What more do you need?
     
  6. ann

    ann Subscriber

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    In our lab we have it turned up toward the ceiling with a white card used to bounce the light back. The ceiling is low and it is just too bright hanging the "normal" way and when some of us used some warm toned papers they would tend to fog a bit.
     
  7. ParkerSmithPhoto

    ParkerSmithPhoto Subscriber

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    You should check the filters. Mine were all shrunken and cracked, and plenty of unfiltered light would be pouring out of them. Theoretically, the bulb only produces "safe" wavelengths, but at that high intensity I doubt it's very safe for very long. I'll run a test with some MGWT tonight.

    The Rosco gels cost about $8 for a 20x24 sheet, which will give you two complete sets of filters for the unit. You could double these up and/or add Rolux (diffusion gel available in various stops). The #19 is 2.3 stops. I considered the Medium Red #27 as well, but it was so dense and dark purple I figured that it wouldn't be a good choice.
     
  8. michael_r

    michael_r Subscriber

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    I've never used one personally, but my understanding of others' experiences would seem to echo Ralph's comment. Perhaps it depends on the paper, but I remember John Sexton saying unless you close the Thomas WAY down, it is not a very safe safelight. I guess all I can recommend is doing a proper test.
     
  9. ann

    ann Subscriber

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    The filter is fine.

    It is always best to run fog test even with "safelights"

    I am trying to remember which paper, and it was Forte warm grade 3, if I am remembering correctly. I was a bit surprised myself and the fog was slight but none the less still there. I have test our light up to 30 minutes and except for that specific paper no problems.
     
  10. RPippin

    RPippin Subscriber

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  11. Bob Carnie

    Bob Carnie Subscriber

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    I use them as well , at the lowest setting , I have no problem with them.
     
  12. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    I like mine. I keep the flaps closed all the way in my space.

    If you are the sort of person who likes safelights off when focusing and enlarging, then it isn't a good choice, because of the ramp up time, and the current surge might not be so great for the enlarging timer. If you leave the safelight on all the time, this isn't an issue.

    p.s.: Thread title updated, despite my hatred of emoticons.
     
  13. Sundowner

    Sundowner Subscriber

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    I've got a good one that needs the filters replaced. Can someone post a link to where they got the replacement material?
     
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  15. ann

    ann Subscriber

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    good point David, about turning it off. Every once in awhile I have a student hit the wrong light switch then they have to work in the dark for about 10 minutes as it cools down.
     
  16. outwest

    outwest Subscriber

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    To really do a safety test you have to first expose the paper to its threshold point where it will just show in development, THEN do the coin test. As a result, the shutters on my Thomas are closed and the side closest to the enlarger is 2/3 blocked. That made it completely safe for any normal amount of exposure time including burning. I did the test this way after John Sexton called them "Thomas paper burners" in a workshop.
     
  17. Newt_on_Swings

    Newt_on_Swings Member

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    The filters are really easy to replace once you find the gels, a search for the mentioned rosco gels or ruby lith on google will get you sources. You have to be careful about cleaning and disassembly of the glass plates which sandwich the filters. There are 4 of them which slide in, they are wrapped together on the edges with colored tape. Just peel back the tape carefully over a trashcan as sometimes the glass edges may have cracks and shards may break off as glass dust or specs. You can find vinyl colored tape at the dollar store that matches the color edges too, and just wrap everything together.
     
  18. Leigh B

    Leigh B Member

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    Rubylith is red. It will dramatically reduce the brightness of the monochromatic yellow sodium vapor lamp used in the Thomas Duplex.

    Not a good choice IM[-H]O. :confused:

    - Leigh
     
  19. Sundowner

    Sundowner Subscriber

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    Cool. Thanks for the tip. Should be easy to fix with the right filter gels.
     
  20. ParkerSmithPhoto

    ParkerSmithPhoto Subscriber

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    The best place to look would be a local video rental and sales store. Video guys use more Rosco gels than anyone else.

    What I did was slice the existing tape with a razor, and then soak the two glass pieces (per filter) in water. The old gels literally melt in water. Razor off any stuck stuff, wash with soap and dry. I put Rosco diffusion -- Rolux -- in each pane, so one diffusion gel and one layer of the #19 Fire.

    Tonight I flashed some paper to around a Zone VI level, and did another coin test with both MGWT and MGFB. With the unit wide open and the paper at 3 feet, I did start to see fogging at ten minutes on both papers. Even with both panes closed, there is plenty of light in the room, much more than the 15 watt units I was using before. It's nice to be able to see the clock!

    Incidentally, I wonder if some of the reports of fogging from these comes from the fact that the filters are some sort of gelatin. Why else would they melt in water? Could the company have used inferior filters? The Rosco gels are polycarbonate, and I've had some of these for 10 years that have never faded or cracked, unlike what I found in the Duplex: both the gel and the diffusion were paper thin, dry and brittle.
     
  21. ParkerSmithPhoto

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    The Rosco #19 Fire is a very red gel, and despite that, the light that comes out of the unit is yellow all the way.
     
  22. Leigh B

    Leigh B Member

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    The spectrum of a sodium vapor lamp consists of two very narrow energy peaks at about 589 nanometers.

    The transmissivity of the Rosco #19 Fire gel is about 50% at that wavelength, which is the only one that matters in this application.

    Due to its cutoff characteristics the gel will look red to the human eye.

    - Leigh
     
  23. RalphLambrecht

    RalphLambrecht Subscriber

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    ido not likeacentral light in the middle of the romm.because,iseemto end up standing in my own shadowehereever i stand,it is very annoyingtowork in one owns shadow.also,it was not save when tested it wide open!
     
  24. Newt_on_Swings

    Newt_on_Swings Member

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    Well don't forget there are two sets of gels used in the Thomas duplex. The orange set with the vanes open and then the red set with the vanes closed all the way. Ruby lith could be used on this 2nd set for max protection when working with things such as ortho film.
     
  25. Sundowner

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    The diffusion/#19 combination seems like it might work. Thanks for the info!
     
  26. Leigh B

    Leigh B Member

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    If your darkroom is painted white, as it should be, there is no issue with shadows.

    Mine is white, and I can read the label on a bottle with my back turned toward the light, at the other end of the room.

    - Leigh