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  1. #1
    Jim Noel's Avatar
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    Screw-in UV Fluorescent source

    I am looking for a source to purchase some screw-in fluorescent uv bulbs to use in a portable UV box.

    Thanks for your help

    Jim
    [FONT=Comic Sans MS]Films NOT Dead - Just getting fixed![/FONT]

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    Louie

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    DBP
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    Ditto

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    Jim Noel's Avatar
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    Thanks for the help.
    [FONT=Comic Sans MS]Films NOT Dead - Just getting fixed![/FONT]

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    I bought mine from a place called topbulb.com. They charged a lot for shipping, but otherwise I have no complaints.

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    Try Menards if you have one nearby.

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    Couple quick questions:

    - I understand the use of black light UV bulbs. Do standard fluorescent put out enough UV to be useful? Or just stick with blacklights (or specially made UV fluorescent sources)?

    - For the box, is the reflecting material important? I see some people use white. Does something like aluminum foil change UV reflectivity for better or worse?

    - Do you just leave your light source "on" and slide a print under to keep things consistant? Or do y'all use "instant on" of the spirals and call it good?

  8. #8
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    The BLB bulbs emit enough UV to be useful - but they are much slower than BL bulbs. Their lower price makes them worth using to me.

    I did not see any significant difference between aluminum foil and glossy white paint. YMMV.

    I use the instant on. In another thread, Sandy King actually tested and found light intenisty varaiation in the first minute (IIRC) but little after that. In a typical exposure running several minutes, the amount of variation was insignificant for our photographic purposes. I've come to the same conclusion in practice with both salt prints and VDB.
    juan

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    Quote Originally Posted by cperez
    Couple quick questions:

    - Do you just leave your light source "on" and slide a print under to keep things consistant? Or do y'all use "instant on" of the spirals and call it good?
    I was in a Pt/Pd workshop a couple of weeks ago with Tillman Crane. He recommends just leaving the box on throughout the printing session.

    There are two reasons to want to NOT turn off the light source. With traditional fluorescent tubes with magnetic ballasts, there is a problem that some of the tubes may not start when they unit is turned on. Most box designs call for a metal plate that is supposed to correct this problem, but I don't think is an absolute guarantee. I know that Tillman has a problem with his boxes and has to tinker with them a bit to make sure that all of the tubes come on. And once they are on, you don't want to turn them off again.

    CFL's (spirals) have a very pronounced warm-up characteristic, but traditional tubes also have this characteristic. Some months ago I found a report from a lighting technology research group at RPI in which they measured the warmup times - unfortunately, I failed to save it and now I can't find it again - but my recollection is that their conclusion was that while the warmup actually took 2-4 minutues, the light output was reasonably close to the maximum after the end of the first minute. With exposures of 4-12 minutes for various alternative processes, a variation during the first minute probably won't make a big difference. I believe that Sandy King did some tests that confirmed that conclusion. But again, just leaving them on avoids having to worry about warmup.

    The other side of the coin is why would you want to turn them off between exposures. Fluorescent bulbs have a fairly long life expectancy, and their energy consumption is rather low. So economics are not a concern. I suspect that the two valid reasons have to do with the potential risks of leaving the UV source on continuously. One risk is that spillage from the lights could cause paper to be fogged before it is intentionally exposed - having a bare bulb left on continuously in the area where you are coating paper woudl be a bad idea. The other is that you want to minimize exposure of your eyes to UV - unless you like the idea of cataract surgery at an early age. Both issues can be addressed by have a UV box design with a door that can be opened only to insert and remove your printing frame, and left closed at all other times.
    Louie

  10. #10

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    Quote Originally Posted by Monophoto
    I was in a Pt/Pd workshop a couple of weeks ago with Tillman Crane. He recommends just leaving the box on throughout the printing session.
    This makes a lot of sense to me for a workshop enviroment but in my own working conditions it would be a very big waste of energy to leave the tube bank on throughout a printing session. At 12 tubes X 40 watts each that turns out to be almost 500 watts, a fair amount of energy. And there really is no point in leavingthe tubes on all the time as far as exposure consistency is concerned, because tubes reach full output almost immediately on being turned on. Yes, turning them on and off will shorten the life of the tubes somwhat, but that is the only down side.

    The spiral tubes put out a lot of UV light, especialy in the 27 watt size which is now available, but their major downside is that they do not reach full output until they have been on about a minute or so, as others have pointed out. So in this case it would make sense to leave them on for the duration of the printing session. A better procedure, however, would be to connect the sprial tubes to a light integrator.

    Sandy

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