Joel Lewis

I don't know how ac vs. dc power would affect longevity. I would think the main factors causing degradation of the filament would be little affected, but I guess the only way to know would be to experiment.

No -- the  old mining helmets were powered by acetylene gas, released by the reaction of calcium carbide with water. Interestingly enough, an oxygen/hydrogen flame( which was once used to heat a piece of quicklime to incandescence in the old 'limelights') is if I understand correctly about the only small, even somewhat convenient ways without pre-processed fuel( I'll get to that in a second) to reach the temperatures necessary to convert calcium carbonate and carbon into calcium carbide( I believe >3,600 F: Pure calcium requires lower temperatures, but also a production process in itself to produce) without an electric arc furnace, which partly explains why acetylene never caught on at an industrial scale as an alternative to town and later natural gas, despite it's hotter and brighter flame( the bigger issue was it's explosiveness).

A bunsen burner or blowtorch( depending on the fuel) may reach those temperatures as well, but I'm specifically talking oxy/hydrogen because I was thinking of burning the mixture of oxygen and hydrogen gas produced by the electrolytic splitting of water in situ. So it's technically electric and pyro both.  You could try it out with any type of lamp mantle, but the nernst type filament seems as easily come by as and more robust for experimentation than traditional lamp mantles, and better proven for indoor lighting than quicklime. There are literally potato peelers made with the stuff.

It may have to do with regulating current through the filament.

The original Nernst( with a second 'n') lamp required a 'balance' of copper resisters to regulate the current, as the filament becomes more conductive as it's temperature increases. These had to be housed in an oxygen-free environment, so you kind of lost out the back end what you gained at the front, but I suspect this can be surmounted with modern electronics( or even pure bulk of components, which may be what's happening in the video above). Not 100% sure if that was a result of some specific chemistry of their particular filament, but I think it's the nature of the oxide filament in general. Alternatively I would think you could limit the current at the source ( I.E. a serial stick of AAs or a couple of homemade batteries, instead of household mains). They also included 'warmers' on either side of the filament, though the heat of a single match was enough to do the trick, and I've seen claims that the same held true for at least one homebrew experimenter.

Or you could just heat your filament to luminescence directly with an electrolytically derived oxy-hydrogen flame, which may be my favorite option.

Along more 'traditional' lines: Why not consider Edison's original filament as a way around the difficulty in acquiring Tungsten -- carbonized Bamboo? Accessible, Permie friendly, and a documented life of 1,000 hours is nothing to sneeze at given our purpose( namely, to have fun doing it -- er, I mean, survival/off-grid situations)? That's 40 days continuous, 120 on eight hours a day. In a vacuum, on household mains, which means potentially a good bit longer in a neutral atmosphere on lower current. Seems like a very viable 'homebrew' option to me.

First off, hello. *waves*

Second, I think I have the golden ticket to make a practical diy light bulb: an oxide filament. Zirconium Oxide, to be precise - which being an oxide and thus not subject to oxidation, can operate in open air. Google 'Nernst Lamp'.

Here's one YouTube poster's dirt simple homemade 'Nernst lamp'.



Filament was courtesy of a ceramic potato peeler. It really does look that simple: Yes, it needs to get hot to start conducting, but that's acceptable in an off-grid diy( and can probably be made automatic a-la the original Nernst lamp if you're really ambitious).

Pair that with a battery of aluminum can dilute-bleach, or homemade lead acid( or more safely, lead salt) batteries, and you've got everything you need....

Hope this sparks some new experimenting.

PS: Going the more traditional route, Nichromium wire seems like the best bet for any kind of 'readily available' metallic filament, though I wonder how much light can be squeezed out of it.


Joel