Homebuilt sodium safelight?

With the Duklo safelight unavailable in the United States, and the Thomas long off the market, I'm interested in building my own version. What I need to start is a low pressure sodium lamp -- and that looks like the hard part. Outdoor lighting (on which this was based) has converted almost exclusively to either high pressure sodium (more efficient with slightly better color rendition) or LED (any color you like, longer life and lower power consumption per lumen). For darkroom use, however, the nearly monochromatic low pressure sodium is best: it's already very close to the sensitivity minimum for RA-4, as well as being a safe wavelength for multi-grade papers and ortho films. Filters are used to strain out the two or three emission lines away from the primary pair in the yellow, and baffles to limit brightness (especially for RA-4) to give useful safe times.

Problem is, low pressure sodium is just about gone, and I don't know the technology well enough to buy a ballast, socket, and bulb to wire the thing myself (though I can probably learn, if there's no other source).

Where might one find low pressure sodium lighting these days? Replacement bulbs, I see -- but the fixtures?

This guy seems to know:

It's mainly about HPS, but there's some bits about LPS. His entertaining videos have sparked my curiosity in sodium lamps, but I didn't go anywhere with that...

Osram still makes special-purpose Sodium-vapour lamps. Though the data-sheets are a bad joke, even containing a phantasy chem. element

Try Bulbs unlimited, which I believe is in N.C.

I believe this is where I got my 30 watt Thomas Lamp bulb, a match for the original bulb, however, If I can find the receipt, I'll let you know, ASAP.

Be Safe, Be Well, and Godspeed to all.

Your looking for a Philips low pressure sodium 35w clear glass bulb and here is a link to one.

https://www.lightbulbs.com/product/philips-327817 at 51.59, which is what I bought when I needed a replacement.

This vendor also sells entire fixtures, and parts, electronic or otherwise.

I found this same bulb on a second site for $123.** and it seems it is still easy enough to find.

Don't forget, if you're going to make your own Thomas, the two gel filters (a orange red and a tobacco) you'll need to install on the glass panels, Stage shops like ( http://www.barbizon.com/store/category/Dedotec/lamps/stage-and-studio ) to govern the light output, (depending on how many hours you use them, have spares already cut to replace them with, ever so often) alone with the adjustable blinds, and use tempered safety glass plate.

People will tell you this stuff in no cut-able but I have done it with a hardware glass-cutter,(I have better now) and try to use a medium-slow down pressure when you lower the glass against a 90 degree table edge.

CAUTION; In the plate glass I've cut, there is most likely going to be a full length, concave edge, sharp on both sides, and you'll need to be prepared to diamond file or grind these down, at least to the point that you won't cut yourself when rubbing hard against the treated edge.

You can then fill whatever concave that's left, if it bugs you, with high temperature silicon or gaffers tape (Duck tape will get gooey)

I have granite tables in my shop/studio/assembly table, and if you have a piece of hard stone long and wide enough to accommodate your mother piece, use it, as the snaps are crisper,

I hope this help, but I expect you already know what you're going to do, so hopeful, your project will inspire others here to try their hand in a similar endeavor.

Cheers.

I dug around on lightbulbs.com and didn't find them selling a single fixture for SOX bulbs. Replacement sockets, bulbs (35W is cheaper than 18W, guess demand is really low for the dim ones), probably ballasts if I dig further, but not a single actual fixture. This is what I ran into previously -- bulbs are still sold as replacements, but the retailers or manufacturers seem to have decided no one wants LPS, even though it's strongly preferred for certain applications -- astronomers would like to see all street, yard, and other outdoor area lighting in LPS, since it's easy to filter out the light pollution (unlike anything with a reasonably continuous spectrum, which is almost impossible to filter).

I can buy actual Thomas filters at Freestyle, but I'm not trying to replicate an actual Thomas -- I'd probably prefer a simpler fixture, in fact, and the adjustments they have seem like something you'd use once in a given installation, and once it's set up with the intensity and direction of light you want, never mess with again.

One drawback of the Thomas is that you need to leave it on for your session. The shutters are used to dim or black out the light. The chain mechanism is used to do this. I use an Ilford 500 light source on the enlarger and the brightness of the safe light can overwhelm the image when trying to focus. Just something to keep in mind when designing your own or where to place it.

Yes, these work best if they aren't illuminating the area where the enlarger is, or they have some sort of shutter in place.

I have accumulated 4 working Thomas safelights. I use them for color and black and white. I open and close the vanes as needed. There's a lot of information on this site for making your own filters.
The low pressure lamps emit 2 very close emission lines that black and white paper is not very sensitive to.

The trick would be to find a Thomas cheap and make your own filters. For black and white, all you need to do is attenuate the intense light.

Keep it away from the enlarger, you will not be able to focus. These units take at least 10 minutes to warm up.

I've had good luck with color, but the trick is to minimize the time the paper is vulnerable.

Or save the trouble and buy this: https://www.ebay.com/itm/Vintage-Ar...255558?hash=item1f0acdf386:g:uVsAAOSwoBFeOfMH

I found the Thomas safelight was not safe for my darkroom, and got an Aristo red which has worked fine. It's very bright and I like the color better than the sodium vapor light. Note that the one for sale is just red--the yellow tube isn't shown, and the model number doesn't include yellow.

voceumana said:

Or save the trouble and buy this: https://www.ebay.com/itm/Vintage-Ar...255558?hash=item1f0acdf386:g:uVsAAOSwoBFeOfMH

I found the Thomas safelight was not safe for my darkroom, and got an Aristo red which has worked fine. It's very bright and I like the color better than the sodium vapor light. Note that the one for sale is just red--the yellow tube isn't shown, and the model number doesn't include yellow.

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These are nice, I have one, these came out of graphic arts labs, thus the red. You have to keep at a safe distance, but they are beautiful to look at.

The gel filters from a stage supply will be larger, full sheets, about $8 @, if I recall Correctly.

You'd think you would have found at least one fixture at that light center.

If you do build your own, I'm sure I and others here will be interested in seeing the results.

Just so you know, there is a Barbizon lighting shop in Charlotte, off of Graham Street, where you can find no only the gels at good prices, but other stage lichting stands and clamp, as well as bulbs for hot lights.

I've got a small, adjustable stage light, no the kind of thing you see now days in most studios, and they only needed few moments to pull the replacement bulb out of stock.

Call first just to be sure the remain open, I last was there about two years ago and it's been a crazy last year.

I have a couple stage lighting gel sheets that I bought in '04 to do split printing (one blue, one yellow -- got blue because I couldn't find a magenta with enough green cutoff for the Grade 5 or 6 equivalent). I got them from a similar shop in Winston Salem, though I don't know if they're still there.

That Aristo linked above is clearly no use for color (and seemingly not recommended for multigrade, though I've used red with multigrade in the past) -- while LPS can be filtered and attenuated to give a good safelight for RA-4 as well as being safe for graded, multigrade, and most ortho materials.

The other issue I have is a low ceiling in my darkroom (I live in a mobile home): a bulky object with prominent corners hanging from the ceiling is guaranteed to collect blood and hanks of hair over time. I may yet wind up cutting a hole for the condenser lamp house on my D2.

Donald, I believe you could, using metal housing material, build a vertical light, that houses the lamp low down in the up-'box/tubing and use a bend like you see on old ships oversized piping, on deck ( like actors in films liked to hide in comedies, etc), and a reflected sweep, to a 90 degree outlet, where instead of a circular shape, simply projects the top of the surface at a wedge shaped angle, so the light is no only bent, but actually allows the top of the opening to sit near the ceiling, with the main unit either stood up or attached to a wall, with a metal plat or bracket, to protect the wall from heating. You should have a cover over the opening, either a bug proof screen of piece of acrylic, but I think that would, 1) give you the distance automatically, from your set-up to safely expose your enlarger and sink area and, 2) fit withing the tight confines in your space..com

You could even use a narrow vertical, and sweep the opening a bit wider at the top, but it would still require the same amount of foot space, if on the floor.

I'd still use the gels, as per replacement specs for a Thomas Light, if you're going with the 35w lamp, and paint the inside of the housing in white enamel.

A last complication I suggest, is to buy an RC or home alarm,Rechargeable Lead Acid Battery,with charger and buy some pc fans from "The Grid" off N. Tryon, past W.T. Harris Blvd. here in Charlotte so you can have a couple of these running on that battery, so even when you turn off the lamp, the fans will continue to cool the 'box'.

In case you did no know, The Grid is the local Goodwill computer store and you can buy parts, PCs, Kindels, Ipods, Printers, some time inks, and Blackberry Pi computers, etc there.

Other than the micro PCs, it's used equipment, and new, unused inks, etc and a great place to pick up an older but good quality scanner and Printer, as well as Monitors.

I hope this is all clear, and somewhat useful, to you and others.

Be Safe, Be Well, and, Godspeed to all.

Greg Davis said:

California Stainless makes a Thomas Duplex replacement: http://sebastiandarkroom.com/darkroom_products.php

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Apparently if you have to ask what it costs, you can't afford it -- because they don't seem to be telling.

I can get a used Thomas on eBay for about $200 plus shipping, new filters and bulb for another hundred. I'm sure I can beat that by a couple hundred with LED. I had thought I could beat it similarly by building my own LPS, but it no longer seems that way.

Donald Qualls said:

Apparently if you have to ask what it costs, you can't afford it -- because they don't seem to be telling.

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The available Sodium-vapour lamp from Osram that might be used for a DIY project costs here 460€ at the chapest dealer...

Well, at least Osram is selling them in Germany. Here in the USA, there doesn't seem to be any source of low pressure sodium as a complete lamp -- wiring, ballast, sockets, bulb, and reflector/diffusion assembly. High pressure sodium is all over, LED, even the much less efficient metal halide -- but no LPS.

I know absoluetly nothing about this, but stumbled across it on Ebay: https://www.ebay.com/itm/REPLACEMEN...545354?hash=item2174fb464a:g:SCMAAOSwERtfQu4F

An LED replacement for Thomas Safelight bulbs?

This one is considerably cheaper: https://www.ledlightingwholesaleinc.com/LED-8101-p/led-8101-.htm

Donald Qualls said:

Well, at least Osram is selling [the complete luminaire] in Germany.

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No, they do not. When I use the term "lamp", I use it in the technical correct way, meaning just the bulb.
Sorry for confusing you.

AgX said:

No, they do not. When I use the term "lamp", I use it in the technical correct way, meaning just the bulb.
Sorry for confusing you.

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Ah. I wondered about that, but that seems rather high, since I can get the 35W LPS bulbs here for just over $50. Useful only as a replacement if you don't have the ballast, mounting parts, and shielding pieces.

Donald, et al, a large part of the design for a narrow thickness for a sodium LP safe light, can be found pre-built,in the form of a 4-5 foot metal file cabinet, Which many folks just toss out, offer up on Freecycle.com, or Craig's list, or, in thrift shops like Goodwill, etc.

I have a five footer sitting on my back area, waiting to be turned into a standing black board sort of thing, by using one of it's two, wide sides.

You could find a cabinet, like this, or even a gym locker, and, with a standard deep drawer like mine, remove the furniture/fixtures/drawers inside and using a metal cutting tool, or cutting torch, if you're into all the prep and clean-up that requires, cut the remaining rectangle body in two, but leaving the full top in place,so you end up with a full length, shallow box, say 10 inches deep, and a jutting 'hood', ready to be formed into the top of the periscope form I described earlier. Take the left over sheet metal and, after riveting, welding or even epoxying some small angle iron, to the inside edge of the opening, up to let's say, 12 inches below the top, and one joining piece to bridge between the two uprights, with the open angle, facing outwards.

Then you can line the angle iron with good wool felt, as a light trap, and hinge a full width door, with rivets or a weld,

I should mention, that a second strip of the same heavy sheet needs to be run around the inside of the door edges, or better yet, the same small angle iron reversed to mate with the cabinet irons and felted, also, to really light proof, welded together, so the edges will no twist.

If you need help with the angle Iron welding, a local High School, or Community College welding shop instructor will usually be happy to lend a hand, in my experience.

To form the extended hood, mate a lower extension shelf at the the iron cross piece, jutting forward, and, i pre-fit a wide "U" shaped section of cabinet steel,, and , if needed, support the forward edges, with more small angle, so you have a ready made fitting for the filters, and glass.

At this point, you'll want to use a clean, white enamel to the inside surfaces, install a mirror or a sweep, in the top hood to bend the light to 90 degrees, so your light is projected out the top into your work space, and finally, take a piece of steel panel, bend it into an upside down "U" shape that fits snugly inside the cabinet, and us it as a base to install your fixture and lamp.

Home depot sells 4" square, real rubber pads, in two-packs and I suggest you buy some and glue up some isolating pads to go on the supporting fixture, so it is well insulated from conducting any electricity to the cabinet housing, so all is safe, and these rubber insulators stay between the inner and outer unit.

Where you place a couple of computer fans, powered by a rechargeable lead acid battery, with it's own on off switch, (a used wall panel light switch will serve) to force cool air into the bottom of the cabinet is your decision, and there is tons of info here on how to make a light proof louvered vent or two.

Install your switch to turn the LP sodium light on, install the filters and glass hood piece, and mount to your selected wall.

It probably takes longer to to reread these instructions than to build the cabinet, but it should be a simple build, with no a lot of bumps on the way.

If you are having difficulty finding the fixture, etc for the Lamp, I suggest an Architectural Supply house, which carries used everything, building related, and see if they have what you need. You can get your louvers there to, if no Habitat stores.

There used to be a very good one in Charlotte, years ago on South Blvd, but I would no be surprised if they moved into the surrounding townships.

I hope this helps, as the cabinet alone will account for at l3ast 5 feet of distance from your enlarger, even if you mount it onto the ceiling, which I do no recommend without heat proof insulators between the unit and the ceiling, being a bit paranoid myself, of electricity and heat together.

IMO, this is likely the best design for a sodium lamp in a small space an you only need a couple of extra feet distance from your working stations, to be safe.

@eli griggs That sounds sort of like the "easy way" to put a V-8 into my Fiesta. "Start by taking out all the engine, transaxle, suspension, and brake parts, front and back, then pull out the dash, steering wheel and console to make room to cut away two thirds of the firewall."

Honestly, I'd be ahead to just work in the dark, or try to find (or build!) some print drums, before going to this kind of length. I'm not set up to do this kind of work, especially since my move (all my shop equipment is in storage).

I could buy a Duka 50 on eBay for $100 to $150+, plus shipping -- but a new bulb for those costs $300, and as far as I've been able to find, there's only one left. ANYWHERE. The same may be true of the more common LPS bulbs by the time I'd need a replacement.

If space is an issue, why not just use several smaller standard safelights? Just light the corners of the room maybe?

That question asked, I do have an extra Thomas Duplex sitting on the shelf. It needs a bulb. Also needs the filters replaced but I have the correct gel filters in stock as well. PM me if you are interested.

Thanks, @ParkerSmithPhoto but I'm pretty sure a Thomas is a bad idea with a ceiling barely high enough to install a standard door. Hang it with enough clearance to open and close the windows, and it'll be waiting to prey on my scalp. On might make a good source of the electrical and mounting parts for the LPS, but I'd still wind up building a whole new housing to put it all within, at most, a foot of the ceiling.

Donald Qualls said:

Thanks, @ParkerSmithPhoto but I'm pretty sure a Thomas is a bad idea with a ceiling barely high enough to install a standard door. Hang it with enough clearance to open and close the windows, and it'll be waiting to prey on my scalp. On might make a good source of the electrical and mounting parts for the LPS, but I'd still wind up building a whole new housing to put it all within, at most, a foot of the ceiling.

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Well I love my TD but if I was in your situation, I'd just bounce a few small safelights off the wall. You can use the ROSCO Fire #19 gel to upgrade any older lights where the filter might be suspect. If you go down the rabbit hole of DIY a new safelight, you might end up spending the next year building instead of printing.