Candles are one of the oldest forms of generating light. Any flame, of course, is a source of light so candles emerged from a search for materials that could burn for a long time. Nobody knows who first noted that beeswax, beef tallow or spermaceti from whales burned well, but it would not have been a difficult thing to notice. Countless people must have observed that the fatty parts of animals when cooked would sometimes catch fire.
Until the early part of the 19th century, candles were made by covering wicks with beeswax, tallow or spermaceti, but as the chemical industry got going, stearic acid became more and more available. This acid is formed when animal fats are broken down by the action of an alkali, such as sodium hydroxide. The stuff that forms in this reaction, sodium stearate, is soap. When sodium stearate is treated with an acid we get stearic acid. It turned out that stearic acid burned well and could be produced cheaply. It was great for candles, except for one thing. It was brittle. This problem was solved by adding some paraffin, a mixture of long hydrocarbon molecules, which was isolated from petroleum.
Now the problem was that the paraffin made the candle wax melt more easily and the wax would drip down the side to make “waxicles.” To make a dripless candle, the wax has to have a high enough melting point so that the heat of the candle is not enough to melt the edges. How do you do this? By increasing the amount of stearic acid. Of course, you can just design a candle so that the edges are far from the flame. A big candle will not drip. The thicker the candle, the less likely that the flame will melt the edges.
But here's another little trick to making dripless candles. Pour some water into a bowl and add a couple of tablespoons of salt. Soak ordinary candles for a couple of hours and presto, you’ll have dripless candles. How? Because the salt absorbs into the wax which in turn raises its melting point. But if you want a really interesting candle, you’ll have to get hold of a dried stormy petrel. That’s a bird that lives in the Shetland Islands and has a very high-fat content. Islanders have by threading a wick through its beak and fixing its feet in clay and then burning the bird. But I bet the bird drips.
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