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12/31/2011 / thriftomancer

Repurposed Oil Lamps

Before we begin, if you haven’t already read my last post on Fire Safety, go do that now. It’s all important info, but for this project it’s vital that you know how to deal with a grease fire. Now…

Oil lamps are an ancient and effective way of keeping the Grues at bay throughout the night. They’ve literally been used since the dawn of settled civilization. They’re also ridiculously simple to make.

All you need to make an oil lamp is a quantity of flammable liquid (olive/cooking oil, kerosene, garlic dipping sauce- you’ll see, ect.), a (preferably lidded) container for said liquid, and some sort of natural fibrous material to serve as a wick (braided twine, twisted paper, a long cut strip of sock, ect.).

You’ll likely need to make adjustments to how much oil is available and the size of the wick before your lamp will burn steadily, but as you follow the basic formula of liquid fuel + container + wick you will eventually have some success.

(Note that those ingredients sound very like the description of a Molotov cocktail. I shouldn’t have to say this, but please don’t throw oil lamps. Also, if you’re dumb enough to try using gasoline as your liquid fuel, do it outside.)

The basic method of creating an oil lamp is you take your chosen container and poke a hole in its lid large enough to admit the wick you plan to use. Insert the wick so about an inch sticks out above the lid and the rest hangs to soak in the oil. Fill the container with oil, let the aforementioned wick soak for several minutes until it’s saturated, then light it up.

It’s a quick, easy project that’s useful to boot.

What’s that, you say? You want an actual tutorial with numbered steps and photos? Well lucky for you, these fine folks have made just that. Here are a few lovely, in-depth tutorials on how to make oil lamps from:

Read over those, then come back here because I’m about to lay down some science and show you what I did to troubleshoot my lamp when it just didn’t want to cooperate.

All right. Now that you know what you’re doing, let’s talk about why you’re doing it. How does the lamp you’re about to make (or making right now, I guess, unless you’ve already made it) work? Well, that has to do with a few scientific concepts. Combustion is one of them, of course, but I’ve already gone over that one at length so I won’t bother with it here. Stuff burns and we get that.

The driving concept here is capillary action, which is a property of liquids where they can be spontaneously drawn up through very narrow passages, such as the spaces between individual fibers in fabric or string, against the pull of gravity. In oil lamps, this phenomenon is what draws oil up the lamp’s wick to be burned.

It works due to the interaction of cohesion and adhesion (properties of the liquid involved) with the molecules of the material making up the passageway.

Simply put, cohesion is a material’s ability to stick to itself and maintain integrity as a continuous piece of stuff while adhesion is a material’s ability to stick to other substances. Working together, cohesion and adhesion make it possible for the oil in your lamp to travel up the fibers of the lamp’s wick in a continuous column of fuel to be burned at the top.

The next concept has to do with flash and ignition points. I mentioned before  that the flash or ignition point of a substance is the specific temperature at which a certain liquid or solid respectively will ignite. What I didn’t talk about was what happens when materials with different points combine and are burned together.

You might have wondered before why the wick of a candle or oil lamp can support a flame and not burn itself away. The answer is that the wick and oil have different flashpoints. In both oil lamps and candles it’s the liquid oil or wax that sustains the flame. That fuel has a much lower flashpoint than the wick, so it will combust first and be replaced by more liquid fuel before the wick is ever touched by fire. This leaves the wick a little sooty and charred, but mostly unburned as long as there is oil or liquid wax available for the flame to consume.

In short, the wick draws oil up to the flame via capillary action to serve as fuel. The oil’s higher flammability causes it to burn first, allowing the wick to continue drawing fuel until the lamp’s oil reservoir is empty.

Makes sense, doesn’t it?

Now, let’s troubleshoot. Or, more accurately, let’s look at how I messed up and then fixed the problem.

This is the lamp I made.

Oil Lamp - Unlit

Isn’t it adorable?

As you can see, it’s a repurposed baby food jar (useful things, those) filled with approximately 2 tablespoons of olive oil. I picked this specific container because… Well, because it already had a sizeable hole pierced in the lid. I’ve no clue why. My other reason was that, being so small, I could use it as an experimental mini-lamp to see how long and well the oil burned without wasting a large quantity should something go awry.

It worked pretty well.

Oil lamp with small wick

But it could’ve been better. This is the point where I ran into problems and where you’ll likely do most of your troubleshooting as well.

Take a look at the wick in that photo. It’s four strands of cotton twine braided together and soaked in oil. Wondrously flammable, but not thick enough to carry the amount of fuel that this lamp needed. The wick burned down to the lid, where it extinguished itself against the metal. (I tested to make sure the problem really was with the wick’s oil-carrying capacity and not just general flammability by removing the wick from the lamp and burning it alone. It reduced itself to ashes, so I could be sure the wick’s size was the issue, not the flammability.)

If you run across this problem yourself, the fix is making a thicker wick. I braided a new wick out of the same twine, only this time I used twelve strands instead of four. For comparison:

Lamp Wicks

Turns out that increasing the fuel delivery to a fire by three hundred percent solves the problem.

This is the lamp burning with the new wick. The flame is much larger and, more importantly, didn’t flicker wildly or extinguish itself like during the first try.

Oil lamp with large wick

I let it burn for about 45 minutes, during which time it used about a third of the original fuel. When I put it out the glass was warm to the touch and the metal lid was hot, which makes perfect sense, so be careful.

(Side note: That steel background you see in both the ‘lit’ photos is a three quart saucepan I used as a reaction chamber. Since I had no idea how well or not this project would work, I wanted to be able to quickly smother my mess with the pan’s lid and be done if things went south.)

That’s really all there is to it. Just fiddle around with different gauges of wick until you find one that works reliably and stick with it. (Technically you’re manipulating the ratio of fuel available to the oxidizer and heat present, but you knew that because you’ve been paying rapt attention, right?) It helps to take notes, especially if you plan on making several lamps, but the first step is always rolling up your sleeves and setting things ablaze.

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