I would like to have electric light bulbs. One should be at least as good as a candle.

What we have:

  • The technology level is generally early 1300s
  • But we can create copper wire
  • We have a sufficiently large AC or DC power source.
  • We can also tweak biology a little bit
  • Abnormally good mineral deposits of whatever we want.

What we don't have:

  • The ability to create vacuum bulbs
  • Very fancy glasswork of some other form

Does anyone have any ideas on how I can create electric light (or at least long-lasting, self contained non-open-flame light)?

  • $\begingroup$ You say you don't have "very fancy" glassworks, so am I correct to assume that you have "at least" some kind of glasswork abilities!? $\endgroup$ Commented Nov 25, 2019 at 7:31
  • $\begingroup$ @PiggyChu001 Correct. Again, for most part technology is around 1300s, or late middle ages, which had lots of glass, though crude by modern standards. $\endgroup$
    – Roman
    Commented Nov 25, 2019 at 7:39
  • $\begingroup$ Is the inability to create fancy glass and vaccum a technological problem or is it natural/magic/time travelling issue? $\endgroup$ Commented Nov 25, 2019 at 8:59
  • $\begingroup$ Possible duplicate of worldbuilding.stackexchange.com/questions/109900/… $\endgroup$
    – nzaman
    Commented Nov 25, 2019 at 12:06
  • 2
    $\begingroup$ Dr. Stone anyone? $\endgroup$
    – Aequitas
    Commented Nov 26, 2019 at 3:28

6 Answers 6


The key here is "•Abnormally good mineral deposits of whatever we want."

What you want is a large deposit of Silicon Carbide (e.g. moissanite) in reasonably large/pure crystals. If decent crystals are not available, find a supply of Argon, and use the Lely method to grow them - while this requires high heat, you should be able to use your copper wire to make an induction furnace, and to find a deposit of Graphite from which to craft your crucible.

You take a crystal of Silicon Carbide, about 1mm3, and attach it between two wires. Apply electricity.

Congratulations, you have just created a primitive Light-emitting diode!

By doping the Silicon Carbide with Nitrogen, Boron, and Aluminium, you can adjust the colour of the LED, for a soft white glow. Unfortunately, pure Aluminium will require you to develop further processing methods

  • 1
    $\begingroup$ Could you postulate how bright a crystal of that size would be? There doesn't seem to be much about it out there. The best info I have to go by are a few home videos showing a dim yellow light on very fractured sample $\endgroup$
    – Roman
    Commented Nov 26, 2019 at 5:52
  • 2
    $\begingroup$ @Roman Nowhere near as bright as a candle. Light emitting diodes work great for indicator lamps, but scaling them up to illumination is quite a challenge, and SiC LEDs in particular are 1/10th to 1/100th as bright as the (non-illuminating) LEDs you're used to. They are very simple, though. $\endgroup$
    – Luaan
    Commented Nov 26, 2019 at 7:41
  • 1
    $\begingroup$ @Roman Collaborative work by Linköping University and the Technical University of Denmark (published in Nature in 2017) has produced SiC LEDs capable of 12 times "base" luminescence, and included creating a useable modern light-bulb made of 7 such LEDs. Much like with Cumbrian Graphite (still the only such large-scale graphite deposit ever found!) for pencils, an especially suitable/superior mineral vein that produces bright SiC LEDs could be found. $\endgroup$ Commented Nov 26, 2019 at 8:56

Developing a durable incandescent filament takes decades of patient and expensive effort. But you can get an arc light working on almost the first try.

Since you lack the technology to distill separate gases from the atmosphere, your arc must burn in air. This limits you to the carbon arc lamp. The good news is that these can easily be produced in any historical age where electricity is available.

From the Wiki article: In a carbon arc lamp, the electrodes are carbon rods in free air. To ignite the lamp, the rods are touched together, thus allowing a relatively low voltage to strike the arc. The rods are then slowly drawn apart, and electric current heats and maintains an arc across the gap. The tips of the carbon rods are heated and the carbon vaporizes. The carbon vapor in the arc is highly luminous, which is what produces the bright light. The rods are slowly burnt away in use, and the distance between them needs to be regularly adjusted in order to maintain the arc.

Arc lamps produced in our world tended to be large and mainly suitable for lighting public spaces. Some research and development would be required to make efficient lamps sized for illuminating a private room.

  • $\begingroup$ You will find exactly this scenario, in the middle segment of "A Canticle for Liebowicz". $\endgroup$
    – nigel222
    Commented Nov 26, 2019 at 11:02
  • $\begingroup$ Where do you get carbon rods in 12th century? $\endgroup$ Commented Nov 26, 2019 at 11:18
  • 1
    $\begingroup$ @TomášZato : If we can have "abnormaly good mineral deposits of whatever we want", we can humbly ask for athracite coal and heat it without air to make coke. Chinese had coke furnaces as early as 11th century. $\endgroup$ Commented Nov 26, 2019 at 11:43
  • $\begingroup$ @MartinGrey Will it not fall apart? Or be to brittle to survive the pressure and vibrations of the arc? $\endgroup$ Commented Nov 26, 2019 at 12:01
  • 1
    $\begingroup$ @Tomáš Zato: How do you think carbon rod electrodes are made today? Coke, charcoal, or even lamp soot, grind to powder, place in a mold under mechanical pressure, bake and cool several times. $\endgroup$ Commented Nov 26, 2019 at 12:24
  1. Make a glass "tube" of decent size.

  2. Make a glass "disk" with 2 holes in it.

  3. Make 2 copper wires probably 1 to 2 inches long.

  4. Tie a bamboo fiber between the ends of the copper wires and seal it with a tiny drop of glass.

  5. Thread the wires through the holes (one each, but not all the way) and seal the disk to one end of the tube.

  6. Make a "cloth" piston with diameter "a little bit" bigger then the inner diameter of the tube. (Probably wet a piece of cloth and wring it as tight as possible and let it dry as is)

  7. Push the piston all the way in and seal the holes with fire.

  8. Pull the piston out (not all the way) and seal the neck before the piston end.

Voila! You have a "vacuum" (surprisingly) light bulb.

But of course, it's going to take some skills to seal the neck while the piston is at the mouth (not yours XP) and NOT breaking the glass or burn the cloth or something.

Hope this fits your standard!

  • 1
    $\begingroup$ Tungsten wasn't known untill 1781 though.but the first light bulbs used bamboo (carbon) fibers, that worked decently enough. $\endgroup$
    – Borgh
    Commented Nov 25, 2019 at 8:38
  • 1
    $\begingroup$ But the OP said that they have "Abnormally good mineral deposits of whatever we want". So I assume that includes "tungsten". XP $\endgroup$ Commented Nov 25, 2019 at 8:40
  • 5
    $\begingroup$ Yes, but going from mineral deposits to workable metal is..quite the leap. Especially if you can't even make fancy glassware or have a good vacuum. $\endgroup$
    – Borgh
    Commented Nov 25, 2019 at 8:43
  • 4
    $\begingroup$ Incidentally, really good vacuum is easy to make if you have glass and mercury: en.wikipedia.org/wiki/Sprengel_pump $\endgroup$
    – RomanSt
    Commented Nov 25, 2019 at 16:27
  • 2
    $\begingroup$ In concept, modern light bulbs are simple glass bubbles sealed with wires with a filament between them, then evacuated of most air. It's not fancy glasswork even when made by hand. It could easily have been made in the 1300s if somebody thought to do it. If you included a compound that would soak up the oxygen in the sealed bulb, like a packet of iron filings, you wouldn't need a vacuum to remove it. Char the bamboo fiber first and it likely will not be burned up in the manufacturing process. $\endgroup$
    – Suncat2000
    Commented Nov 25, 2019 at 19:00

Put two filaments in the glass bulb. Wired separately. One filament is magnesium. The other filament is tungsten and will provide the light. First, apply a huge voltage to the magnesium filament causing it to burn and consume all of the oxygen in the bulb. Second, apply just enough voltage to the tungsten so it glows. DONE.


Find a deposit of fine clay made of tourmaline (I can't seem to find its mineral name quickly). Chemically deposit a thin layer of silver (thin enough to see light through) on two sheets of flat glass. Put a very thin layer of the tourmaline clay between the two silver layers, then apply a voltage to the metal layers. At around 100+ volts, the tourmaline will begin to emit light that will be visible from both sides of the glass sandwich.

It may take a few tries to get a working electroluminescent panel this way, but eventually you'll have a dim, blue-green light that draws very little power and can operate literally for decades continuously. You will need an alchemist who can silver a glass mirror, however.

  • $\begingroup$ Silvering a mirror isn't hard, if you can make Nitric acid. Thence, silver nitrate, that will spontaneously deposit silver onto glass. Getting flat glass will be the greater challenge. Although for a small flat, floating molten glass on an iron crucible of molten tin (or lead?) in a furnace ought to be do-able. I do wonder why it was never done back then. No imagination, or a snag meaning it doesn't work in practice? $\endgroup$
    – nigel222
    Commented Nov 26, 2019 at 11:12
  • 1
    $\begingroup$ For both float glass and chemical silvering, the techniques simply weren't discovered, in our timeline, until the 18th century. In my experience, other silver compounds work better for silvering -- I've had heavy silver layers deposit from used photographic fixer (sodium thiosulfate reacted with silver halides) as the fixer oxidizes over time -- but if you want it quickly, you need to make an ammoniacal solution from the silver nitrate, and then add an organic reducer (sugar works). Providing you don't blow yourself up... $\endgroup$
    – Zeiss Ikon
    Commented Nov 26, 2019 at 12:07

Why do you say no vacuum? There's a very simple vacuum pump that can be made with 1300s tech:

Make your bulb, attach a glass pipe that is more than 1m in length. Fill the whole thing with mercury. Let the mercury drain down the pipe. This will leave a vacuum in the tube. Melt the tube together. Presto, vacuum tube.


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