Safe Light once owned by Flash Gordon?

I am pretty sure that this safe light (see below) was used by Flash Gordon in his battles with the Merciless Ming. It weighs a ton and has a bulb in it that has probably not been manufactured since the Crimean War (not the current one), but it does light up!. It has two lids, each one with a piece of glass fixed in place. One looks like diffusion glass, the other is black with random silvering on it. Under each is another piece of glass with an orange filter sitting on top of it.

Any ideas who made this? Is it still useful or recoverable? I can imagine that when that light finally dies, it will be impossible to find a replacement. At the very least, it will make a terrific Halloween ornament (I took one photo with no room lights on and no flash. It's pretty spooky!).

That is a Thomas duplex safelight. It is sought after by some and worth some money. And, yes, replacement bulbs and filters are still available.

http://jbhphoto.com/blog/tag/thomas-duplex-super-safelight/

http://www.freestylephoto.biz/pdf/product_pdfs/thomas/THOMAS_DUPLEX_SUPER_SAFELIGHT.pdf

These safelights were used in professional darkrooms. The sodium vapor bulbs produce a lot of light. The spectrum consists of a series of two thin lines. The filter cuts out all but a doublet in the yellow-orange region of the visible spectrum. Life expectancy for these bulbs is typically 30,000 hours so these safe lights last practically forever. The ones that I have seen have baffles to cut down of the light output. This is probably necessary for use in a home darkroom.

http://www.indiana.edu/~geol105/images/gaia_chapter_1/visible_light_spectral_emission_.htm

A properly set up Thomas safelight will give you a safe light level sufficient to read a newspaper in your darkroom while your print develops in a tray.

Assuming your eyes are good.

Great safelight. I have 2 of them.

Yes...

A Duplex model low-pressure sodium vapor (LPS) safelight, manufactured by Thomas Instrument Co. The unit itself is now discontinued. But here is at least one source for both new LPS bulbs and filter sets from Freestyle:

Thomas Duplex replacement parts

Note that the bulb itself is also available generically for less money from commercial lighting supply outlets. There is also still listed as available new a comparable unit from California Stainless Mfg. It's called a Sebastian Darkroom Products Model OC-1012 Safelight.

Filtration is required because the LPS bulbs incorporate a Penning gas mixture to assist with striking the lamp. The pure orange-colored sodium doublet output lines are themselves safe, but the additional argon and neon in the Penning mixture contributes unwanted blue and green spikes to the aggregate output spectrum, which must then be suppressed in normal use.

The unwanted blue/green spikes may be clearly seen in this illustration at 450nm (faint blue), 498nm (stronger blue), 515nm (faint green) and 569nm (stronger green). Note that this illustration contains a mixture of two light sources, low-pressure sodium (Na) and mercury (Hg), which are overlapping.

Ken

Here's a fun trick for the kids...

Fire up the Duplex and let it warm and stabilize. Then turn on the regular white lights in a closed room. Hand the child something very colorful to look at. I used one of my Sports Illustrated magazines. Tell them to keep their eyes on the object.

Then switch off the white light.

The sodium light is monochromatic, so all of the perceived color the child is staring at will instantly vanish into shades of black-and-white. Or actually shades of black-and-orange. Ask the child to point to a specific color, like blue or green. They will try to do this from memory, while fooling themselves into thinking they are still seeing the full colors from a moment earlier.

Then switch the white light back on.

All of the colors will magically reappear, and the color they are pointing at will almost always be the wrong one. My young son was freaked out the first time he saw that, and demanded an explanation.



Ken

Last year I turned down an offer for two of these free, but I said no because I do not have a place where I can mount them to use. I told the owner to find someone who could use them.

Yes, that lamp should be available easily.
But it needs a special power supply and I do no see such within the light. Is it hidden inside?

AgX said:

Yes, that lamp should be available easily.
But it needs a special power supply and I do no see such within the light. Is it hidden inside?

Click to expand...

It is internal.

I've printed in darkrooms with these safelights twice and really dislike them because they're SO bright that it makes focusing difficult and they can't be shut off for focusing and composing on the easel because they need a warm-up period.

BobMarvin said:

I've printed in darkrooms with these safelights twice and really dislike them because they're SO bright that it makes focusing difficult and they can't be shut off for focusing and composing on the easel because they need a warm-up period.

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I do like the idea of a very bright safe light, as long as it is truly safe, but that is a good point, Bob. My darkroom is about 10ft x 15 ft. I can position this light so it is about 8 ft from the enlarger. If it is still too bright for focusing, I suppose I could mount it so it could swing around a little and thus give less light while focusing.

If it is too bright you can always add a layer of Ruby Lith or neutral density film to the filter packs.

Or even more simply, just cut two pieces of black mount board the same size as a filter. Slide one each into the filter slots on the undersides of the movable vanes. Then one can control the light intensity by progressively opening and closing the vanes with the chain.

Close the vanes completely and the room becomes almost completely dark for focusing. Open them completely and one can read the fine print on a medicine bottle.

If your spectral setup requires use of a second set of filters in the vanes, just remove those and lay them on top of the filters in the body.

And as far as warm-up times being a hindrance, this safelight is designed to be left on for the entire printing session. One only needs to switch the white lights off and on. If fogging over extended time is an issue, then one hasn't yet filtered out those neon and argon spikes.

Or just do as I do. I often have paper out in the easel for extended periods. I've always kept a sheet of black mount board around and in between exposure steps I always lay it across the entire easel so it doesn't touch the paper. It's a habit I picked up decades ago working in a commercial darkroom.

Ken

"One only needs to switch the white lights off and on"

Quite true, but some of us prefer to switch the safelight off when the enlarger lamp is on, for ease in focusing and composing. There must be a lot of us, since many timers have a provision for this.

BobMarvin said:

"One only needs to switch the white lights off and on"

Quite true, but some of us prefer to switch the safelight off when the enlarger lamp is on, for ease in focusing and composing. There must be a lot of us, since many timers have a provision for this.

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Fair enough. So then perhaps this particular piece of commercial grade equipment is not a good match for your situation.

I was just trying to point out that the three biggest knocks against this safelight—that it can't be instantly switched off and on, that it fogs paper because it's too bright, and that it hinders pre-exposure composition and focusing—are not insurmountable problems. They are simply usability issues for an industrial grade versus a consumer grade product. Issues that are easily mitigated if one understands what's going on.

The safelight was designed and intended to be left on over long periods, as striking the lamp is not an instantaneous process, and full warm-up to safe light output usually takes 10 minutes, or so.

If the frequency of light emitted by any safelight is a proper safe match for an emulsion, then it doesn't matter if the light intensity is bright or dim. Safe is safe. The Duplex will fog paper. But not because it's too bright. It fogs because small amounts of blue and green are emitted by those Penning mixture gases, argon and neon. Filter those small spikes of unwanted colors out and the fogging vanishes.

And dimming the intensity for reasons of composition and focus is as simple as I've detailed. In a one-person darkroom, reaching up to adjust the vanes cannot be easier, and affects no one else in the room. It's also possible to simply preset the vanes at a happy medium and never touch them again.

Ken

The OP's safe light needs to be mounted on a ceiling, a very high ceiling. So an industrial building would be a better place for it than a home with lower ceilings.

In my basement darkroom with matt white ceiling tiles...

8-feet 08+7/8-inches = floor-to-ceiling
5-feet 01+1/4-inches = easel-to-ceiling (vertical)
5-feet 10+1/2-inches = easel-to-Duplex (angled from easel to ceiling directly above the Duplex)

Using the above parameters I have performed pre-threshold-exposure safelight tests out to 30 minutes with no sign of fogging using Kentmere Bromide #3 graded paper.

The Duplex was correctly installed regarding hanging distance from the ceiling, and was properly filtered using custom-made Roscoe #19 Fire filters. The vanes were wide open, but blacked out. The test was performed at the easel.



Ken

It just occurred to me then that this type of safelight would not be very good for exposure meters that get confused if there is light other than the exposure light.

Sirius Glass said:

The OP's safe light needs to be mounted on a ceiling, a very high ceiling. So an industrial building would be a better place for it than a home with lower ceilings.

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Heck, that is not possible in my case. What about putting it about 5 ft off the ground, on an angle away from the enlarger. It is very bright!

cowanw said:

It just occurred to me then that this type of safelight would not be very good for exposure meters that get confused if there is light other than the exposure light.

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If the light from the safelight is "safe" for the paper, then it should be "safe" for the meter. If the meter were skewing its readouts by reading additional colors of light to which the paper was insensitive, then it would be useless for calculating paper exposures.

Ken

Sirius Glass said:

Last year I turned down an offer for two of these free, but I said no because I do not have a place where I can mount them to use. I told the owner to find someone who could use them.

Click to expand...

Sirius Glass said:

The OP's safe light needs to be mounted on a ceiling, a very high ceiling. So an industrial building would be a better place for it than a home with lower ceilings.

Click to expand...

Doc W said:

Heck, that is not possible in my case. What about putting it about 5 ft off the ground, on an angle away from the enlarger. It is very bright!

Click to expand...

That is why I passed on the offer of two of them at no cost. At 5 feet off the ground I would have to put it on the other side of the room.