The Chemical History of a Candle

Jennifer Ouellette:

In particular, Faraday gave a series of famous Christmas lectures each year at the Royal Institution — a tradition that continues today. One of the earliest, on the chemistry and physics of flames, became a popular book: The Chemical History of a Candle. These lectures were a gift that Faraday gave year after year to those who showed up to receive it: the gift of wonder at the natural world that continues to surprise us, even today, with its mysterious workings.
Faraday opened with a discussion of how candles were made, from naturally occurring candles like the paraffin and bits of candlewood found in Irish bogs — “a hard, strong, excellent wood” –to manmade dipped tallow candles, beeswax candles, and something called a  sperm candle, “which comes from the purified oil of the spermaceti whale.” He even displayed a candle salvaged from the wreck of the Royal George, which sunk at Spithead on the 29th of August, 1782; yet the candle still burned brightly when lit.
As Faraday described the process:

“The fat or tallow is first boiled with quick-lime, and made into a soap, and then the soap is decomposed by sulphuric acid, which takes away the lime, and leaves the fat rearranged as stearic acid, while a quantity of glycerin is produced at the same time. Glycerin—absolutely a sugar, or a substance similar to sugar—comes out of the tallow in this chemical change. The oil is then pressed out of it; and you see here this series of pressed cakes, showing how beautifully the impurities are carried out by the oily part as the pressure goes on increasing, and at last you have left that substance, which is melted, and cast into candles as here represented.”

The whole post is interesting.