thomas safelight question

phototeacher3000 · Oct 31, 2011

Hi.

I was wondering if a Thomas Safelight can be mixed with red (1A) safelights and still actually be "safe"??

I have a large darkroom/classroom (I am a HS photo teacher) space that has built-in red lights but is too dark for me to feel that my students can function well.

I have a thomas safelight, but am not sure if it'll fog our papers or not.

Thanks!

Roger Cole · Oct 31, 2011

I don't see why not, just be sure to test thoroughly. A Thomas reportedly isn't all that safe in a small darkroom even by itself.

I used to mix my Duka 50 sodium and a Paterson conventional safelight, the Duke on the dry side and the Paterson on the wet side, with no problems at all.

George Nova Scotia · Oct 31, 2011

There are red filters available for the Thomas, it's still pretty bright with them closed. I'm assuming you are using paper that needs red filters.

Either way the usual tests apply.

MattKing · Oct 31, 2011

Welcome to APUG!

There are a few teachers/instructors here on APUG who have responsibilities for darkrooms. You might consider asking a moderator to revise your thread title to include the words "for a school darkroom".

Just click on the exclamation symbol at the lower left of your post, and make your request (to the moderator).

And thanks for continuing to support analogue processes.

Leigh B · Oct 31, 2011

The Thomas Duplex is highly monochromatic* in the yellow portion of the spectrum.

It's extremely bright, since it operates at the wavelength of peak sensitivity of the human eye.

I have mine half closed and can read the small print on bottle labels anywhere in my 9'x12' darkroom (painted white).

We used one in the photo school where I used to teach, and it lit up the whole darkroom quite nicely.

I've never experienced a fogging problem. Graded paper is insensitive to yellow, and VC papers should be likewise. Testing is advised.

- Leigh

*nb: technically di-chromatic, since sodium emits two wavelengths quite close together in the yellow range.

Valerie · Oct 31, 2011

We have a similar setup in our (new!) school darkroom: built in red safelights, and 2 Thomas safelights. Although we haven't got around to testing, there have been no obvious fogging issues.

Newt_on_Swings · Nov 1, 2011

We use one in the darkroom I teach at as well. It is hung up high, and lights up the place very well. We also have individual 5x7" sized red safelights above each enlarger station, they are never used with the thomas duplex on.

I also have a thomas duplex in my basement darkroom, which does not have a high ceiling, but I still keep the vanes open as the walls are not white.

In both situations I have not noticed fog in the time that it takes to expose and develop the print. But it goes without saying, ymmv. test if you routinely keep paper out of box/bag/paper safe for extended periods of time.

Robert Hall · Nov 1, 2011

I have found that I can make it so bright with my safe light that I cant see the image on the paper and it prints perfectly... with Ilford papers.

If I have eastern block papers they will fog quite nicely so I have made rubylith filters for the safe light and use them most of the time.

The red cuts a significant amount of light from the safe lights since they are mostly in the yellow spectrum. So that helps out on both fronts. I still get fogging on papers like Forte and the like if I keep the papers out too long.

It's best to test but as I mentioned, it's pretty safe with the Ilford papers

mgb74 · Nov 1, 2011

Your Thomas safelight should have the glass filters that open and close. If not, I understand they can be "homemade" by sandwiching rubylith film between 2 pieces of glass.

Neal · Nov 1, 2011

Dear phototeacher3000,

Probably. (Nothing beats a test.) We use a combination of them at Chicago Community Darkroom and I've had not issues. Make sure the filters are in good shape though. We got some donations that, if we had used them as-is, would have ruined a lot of good paper.

Neal Wydra

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