This is the third (and, I hope, last) in a series of posts about the Luminiser thermo-electric-generator lantern. This device makes light by converting the heat of a candle to electricity, then using that electricity to run some LEDs.
The claimed output of the Luminser is 200 lumens, or about one-quarter as bright as a “60 watt” light bulb. It’s an impressive piece of technology for $20, and an impressive amount of light from the heat of a single tea-light-sized candle.
But it has a couple of problems. It’s not very stable (sitting on four spindly plastic legs, as shown above), and it uses a disposable, proprietary oil candle as the preferred power source.
I happened to notice that the base of the Luminiser lantern is almost exactly the same size as a U.S. standard wide-mouth canning jar. Which then immediately suggested a solution.
I’ve now fixed both of those issues by converting a standard wide-mouth mason jar into a custom oil candle, just the right size to be used to stabilize and power this lantern. My Luminiser now rests securely on the mason jar, with the candle flame at the same height, and of the same size, to replace their proprietary disposable oil candle.
Here’s the final product, below, where I’ve removed the flimsy plastic legs, and used a low-profile pint (500 ml) canning jar as the base. Plenty of light to work a crossword puzzle with no eyestrain. All that, powered by a flame about the size of what you’d get from a tea light candle.
Directions in brief
Overview
Start with a wide-mouth canning jar (mason jar, Ball jar), pint or half-pint size. Drill a little hole through the metal lid. Stick a little piece of copper tubing through that. Run a piece of cotton kitchen twine through that tube, to form the wick. Fill the jar with lamp oil, screw on the lid, and that’s your oil candle.
(N.B., canning jars come in two formats in the in the U.S., regular and wide-mouth. Wide-mouth is the right choice here, as that fits nicely into the base of the Luminiser.)
That’s the finished oil candle, shown above. This now fits neatly against the bottom of the Luminiser, and replaces the proprietary oil candle.
NOTE: You must also drill a small pressure-relief hole in the lid in order to use this safely. That’s really the only part of this that isn’t obvious. That little pressure-relief hole is a standard safety feature on oil lamps. It is important that you include it in this oil lamp. Even if you skip all the rest of the directions, read that part, in red, below.
Materials:
- Pint or half-pint wide-mouth canning jar, with band and lid (a.k.a., two-piece metal lid). If you’ve read this far, I probably don’t have to tell you, but don’t use a plastic lid.
- 1/8″ rigid copper tubing (sold in 1′ pieces at ACE Hardware, $2, reference below).
- A foot or so of cotton twine, ~2.5 mm diameter, sometimes sold as “butcher twine” (the stuff you’d use to “truss a chicken”, see below for brief discussion).
- For attaching the copper tubing to the lid:
- A few drops of superglue OR
- Optional: A small amount of two-part epoxy OR
- Crazy optional: Torch and solder.
Tools:
- Razor-blade knife (Skil knife) or single-edge razor blade.
- A bit of sandpaper.
- Drill, with bits:
- 1/8″ drill bit (to drill hole in lid for wick-holder tubing)
- 1/32″ (or tiny) drill bit (to drill air relief hole in lid).
- Metal paper clip (to push cotton twine wick through the copper tubing).
Part reference: The only “exotic” piece of material here is the thin copper tubing. My local ACE Hardware sells that, shelved with hobby supplies, for $2 each. It’s “K&S 1/8 in. D X 1 ft. L Utility Copper Tubing“. The metal does not make any difference — copper, brass, or aluminum would all be fine. But the dimension is fairly critical. Don’t go larger, you’ll get too big a flame.
Cotton twine: The cotton twine needs to be small enough to fit through the copper tube, but must fit snugly inside the copper tube. The theoretical internal diameter of that 1/8″ O.D. copper tube is .105″ or 2.667 mm.
You may have to eyeball this, as it’s hard to find twine marked as to diameter, or even as to twine gauge, in the hardware store. Ideally, the cotton twine would run about 3/32″ or 2.5 mm in diameter when lightly twisted. The twine I used was not quite as thick as two U.S. dimes, as shown in the pictures below, thicknesses in millimeters.
What will work: You want 2.5-ish mm cotton twine. Of what I saw on the shelf at my local ACE Hardware recently, this product, labeled butcher’s twine, looked about right.
What might work, but I haven’t tried it: In theory, purpose-made 2.6mm oil candle wicking on Amazon should work, but I can’t say that I’ve tried it, and it’s expensive. If it works, it’ll be a tight squeeze. Separately, a lot of cotton kitchen twine, package-wrapping twine, and general-purpose twine will be too small unless you double it or triple it up before feeding it through the copper pipe.
What won’t work: Material sold as 1/8″ round oil lamp wicking is way too large for this use. Any twine or wicking sold as 3 mm or larger is too large. Wicking or twine sold as 2 mm or smaller would likely be too small. Anything with a “twine gauge” or “size number” in the 10s or 20s (e.g., #12 twine) will be much too small unless you double it up or triple it up.
Finally, you can’t (or, at least, shouldn’t) use twine made of synthetic materials for this purpose, Whether you could use other natural materials (e.g, jute), I have no idea.
Directions in some detail.
1: Prepare the wick holder.
Cut 1.5″ off one end of the copper tube. The simplest way to do this is to place it on a flat surface, place the Skil knife blade or single-edge razor blade on top, and roll it back and forth until the knife edge cuts through the thin copper tubing. Remove the burr around the cut edge by sticking the paperclip in and working it around until you’ve opened cut end back up to the full diameter of the original copper tube.
2: Prepare the wicking.
Cut a foot or two off the roll of cotton twine.
Thread the cotton twine through the 1.5″ piece of copper tubing. First, bind one end of the twine using superglue. Hold the tightly-twisted cotton twine in one hand, put a few drops of superglue near the end, and let it set up. Once set, snip off the little bit of twine past the super-glued part. If you did it right, you end up with a nice, tight, rigid section of super-glued twine that you can then poke into the copper tubing. (Same concept as an aglet, or shoelace-end.) Once you have that started, use the paperclip to push it all the way through.
3: Prepare the metal canning lid.
Sand the plastic coating off a square inch or so of the interior of the lid, right at the center. This is to help whatever glue/solder you use to stick the wick holder to the lid.
Drill a 1/8″ hole in the center of the lid. Wallow it out just a bit. Sand it to remove any burrs.
Drill a tiny hole (1/32″ or so, smaller is better) well off-center, but not covered by the screw-on band that holds the lid in place, to provide air pressure relief. You must provide this pressure-relief hole in order to operate this safely. If you do not do this, and you screw the lid on tight, the oil candle will enter “runaway” mode when you use it. Oil and air expand as they warm up. If you do not provide a pressure relief hole, that will force oil up and out of the wick, resulting in an ever-increasing flame, and possible fuel spill beyond the top of the candle, and a fire.
This tiny vent hole is a standard safety feature on oil lamps, it’s just typically placed so that you don’t notice it on store-bought oil lamps. You may see directions for mason-jar oil candles, or even commercially-offered mason-jar oil candles, that skip this step. The resulting products are decorative objects, not working oil lamps. If you actually want to burn this candle safely, include the air vent, just like a real oil lamp. You may think to yourself, oh, I’ll always remember to leave the lid a bit loose, or some such. But at some point, either you or somebody else will forget to do that. Do your future self a favor and drill that pressure relief hole when you drill the main 1/8″ hole for the wick holder.
4: Assemble.
Poke the copper tube through the lid, so that the long “tail” of wicking is on the under-side of the lid.
Adjust the copper tube until the top of the copper tube protrudes 15/16″ from the top of the lid. This adjustment puts the flame in the correct position. Take the time to get this right.
Super-glue the copper tube in place, front and back, and allow to set. (This is not great technique, but it’s fast, and it mostly works. A more secure method would apply a small amount of two-part epoxy to the back of the lid, around the tube. Or would use a torch and solder to affix the copper tube to the metal jar lid).
Cut the bound end off the cotton twine/wicking, and adjust the cotton twine so that it barely protrudes beyond the end of the copper tube, about 1/16″ to 3/32″ or so. Something under 1/8″. This small amount of exposed wicking will generate a flame that’s the right size. If you leave too much exposed, you will get an unusably large flame, and you’ll have to go back and adjust the wick once it’s wet with lamp oil. You want just a tiny bit of exposed wick.
5: Fill, light, test.
Add lamp oil. To reduce the total amount of oil present, you may want to put some heavy inert filler in the jar, such as marbles, glass weights, clean rocks, or similar. DO NOT OVERFILL. As with any oil lamp, leave space at the top of the jar, to allow for easy expansion of the oil as it heats up. A good rule-of-thumb from canning is, when in doubt, allow a 1″ headspace. Don’t fill it closer than 1″ from the rim.
Insert the tail of the wick in the oil, put the lid on top of the jar, screw the band on to hold the lid into place.
Wait a few minutes for the lamp oil to saturate the wick.
Light and observe. You want a flame that’s maybe 3/4″ tall. Let it burn for 10 minutes to be sure that the flame height remains steady.
Note that the top of the tube is just shy of 1″ above the metal canning lid, and the flame is under 3/4″ tall.
Place the Luminiser over the mason-jar candle and observe another ten minutes to make sure the flame height remains steady.
Below is the final version, using a shorter jar, with the folding legs removed. To remove the legs, take a Skil knife (utility knife) and slice the inside “rim” off the split plastic pegs that hold the legs on. You can then pull those plastic pegs out of holes that hold them to the body of the lantern. Toss the flimsy plastic legs, as they will no longer stay attached to the lantern after you do this.
Never leave the lit Luminiser unattended.
6: Main drawback: Awkward wick adjustment.
A simple oil candle like this lacks the “wick riser” mechanism of a real oil lamp. (That’s the little wheel that you turn to raise or lower the flame.) For this oil candle, you have to adjust the wick height by tugging on the wick and/or pushing on the wick.
As long as you don’t let the wick burn down to a nub, you should be able to grab it with pliers (or maybe even large tweezers) and give it a little tiny pull to lengthen it.
If you overdo that adjustment, you can either stuff the wick back down the tube, using a paperclip, or you can take the top off the jar and pull the wick back down. If you let the wick it burn too far, so you can’t grab it from the top, you have to take the top off and use a paperclip to push the wick up.
It works, but it’s awkward. Luckily, you don’t have to adjust the wick often, once you achieve the right flame height.
If it weren’t for the fact that a wide-mouth mason jar works so well as a stable base for the lantern, I’d probably have bought a commercial lamp mechanism for a mini-oil-lamp, and worked from there. Just to get an easily-adjustable wick. As it stands, the awkward wick adjustment is a minor annoyance I can live with.
7: Eventually, deal with the lantern legs.
The pieces of perforated black plastic in the photo above are the flimsy lantern legs, folded up. At some point, I’ll either remove them, or cut them so that they will fit over the final (likely, half-pint) container, and so hold the lantern firmly to the mason-jar base.
It works fine as-is. Its mostly that those folded-up legs spoil view a bit. Fixing that is optional.
Edit: Done.
Conclusion
The end result is a heavy, solid base for the Luminiser lantern, along with an oil candle that could hold a several-week-supply of lamp oil. This avoids the relative unsteadiness of the original design, and allows you to fuel the lantern cleanly without using the proprietary disposable oil candles sold by the manufacturer.
The fit between the standard wide-mouth mason jar and the Luminiser is so good that it almost looks as if this were made for it. It’s like having an oil lamp with a chimney. Except that the chimney puts out twenty times as much light as the oil lamp itself.
Replacing the pint wide-mouth mason jar with a half-pint would make this more stable, and more difficult to knock over. (The only reason I made this with a pint is that I didn’t have a wide-mouth half-pint available. I plan to replace my pint jar as soon as I can lay hands on a half-pint.) Edit: I have now replaced it with an even better choice, a low-profile pint jar, as pictured near the start of the post). If you desire stability beyond that, epoxy the mason jar to a suitable base, such as a piece of marble or wood.
Finally, let me emphasize the general safety precautions. Don’t run this unattended. Don’t run it with a flame bigger than about 3/4″. (If the flame is too big, pull or push the wick down further into the tube.) Drill that tiny pressure relief hole before you use this, to avoid a runaway lamp situation. For indoor use, burn only lamp oil or kerosene (e.g.,”Klean Heat”).
That said, you do this at your own risk. This is, after all, quite a bit of easily flammable material, all in one place. As with any candle or oil lamp, you always need to keep in mind that you are playing with fire. There is an inherent risk in doing that, and to do it safely, you need to acknowledge that, and take all reasonable precautions.
