Fluorescent Bulb in Darkroom

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I have just spent the last three months pouring most of my cash down the darkroom construction black hole. It turned out great and I am very excited about it. As an aftertought I decided to attach an 18 inch fluorescent light under a cabinet and over a counter for a little extra light. Because of the novelty of the room, I sat in the corner the other night while my girlfriend loaded some film. I noticed after awhile that I could see some very faint glow from the flourescent bulb. This seemed to take at least an hour to subside (we were not in there that whole time in case any of you were wondering). I also noticed that if I touched the plastic cover over the bulb that it would light up where I touched it. Anyone else experience this ? Are there certain bulbs that won't hold this residual light as long ? The film looked ok, but I don't think it would have been if the platic bulb housing had been touched by her hair. Maybe a hairnet will be needed if the light stays. Interesting phenomena.

-- Paul Mongillo (pmongillo@thurston.com), March 02, 2000


Paul, I've always been told to avoid fluorescent lights in the darkroom because some of them have this redisual glow...I think the phosphers still give off light for a bit even when the juice goes away. I just use cheap incandescent fixtures.

-- John Sarsgard (Endive4U@aol.com), March 02, 2000.

I have used fluorescents in a number of darkrooms & have seen the glow and the light from touching the lamps as well. Try putting a few sheets of film nearby and see if you get any fogging. Most likely you are far enough away so that even visible light you see won't be strong enough to show on film in any way. If you are stil worried, put a small cover over the light so you can still have its convenience but cover it when you think it prudent.

-- Dan Smith (shooter@brigham.net), March 02, 2000.

It depends on the tube and the fixture. Kaiser, for instance, makes a Duka 5 Flourescent safe light only for B&W print material.

-- Bob Salomon (bobsalomon@mindspring.com), March 02, 2000.

Paul: The only absolute I've ever heard regarding fluorescent lamps in a darkroom is to avoid them if you process either infrared or very high speed films. They do radiate energy for quite some time after the current has been switched off, but not enough to affect films or paper in general use.

-- Paul Szopa (szopap@missouri.edu), March 02, 2000.

Technically, the afterglow is phosphorescence, not fluorescence, but the effect on your film is the same. There are no general rules: there are many different tubes out there, and they all have different afterglows. In the darkroom I use the ceiling fixtures will noticeably fog RA4 paper up to quarter of an hour after they are turned off.

A standard darkroom safelight test will tell you if your fixture is causing a problem. The afterglow usually has blue or even ultra-violet components, so even ortho-lith film can be fogged. On my RA4 paper tests the 'fogging' showed up as a 5-10cc shift to yellow, rather than a noticeable darkening of the print.

-- Struan Gray (struan.gray@sljus.lu.se), March 03, 2000.

I'm not sure if the new colour matching, high-voltage/high-frequency Xenon filled tubes that you can get these days exhibit phosphorescence to the same degree. Anyone know? Incidentally CRT tubes will glow for a few minutes after being excited by white light too, and most white "Formica" or "Melamine" surfaces exhibit an afterglow as well, but fortunately that decays in seconds rather than minutes.

-- Pete Andrews (p.l.andrews@bham.ac.uk), March 03, 2000.

Thank you all for you comments. I think I'll play it safe and replace the fluorescent light with an old aquarium hood I have in the garage.

-- Paul Mongillo (pmongillo@thurston.com), March 03, 2000.

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