Although candles as timekeepers were known and used until quite recently, the “candle clock” of the Islamic world stands out for its qualities of unusualness. As described by Al-Jazari, Islamic candle clocks worked on the following principle. Each design specified a large candle of a uniform cross section and known weight. So precise were these Islamic candlemakers that they even calculated the weight of the wick! The candle to be used as a clock was installed inside a metal sheath, to which a cap was fitted. The cap was fashioned to be absolutely level (flat) by turning it on a lathe. It was provided with a hole in the center, which on the upper side had an indentation around it.

The burning time of the candle was also known. As it burned, it bore against the underside of the metal cap and the wick passed through the hole. Wax collected in the indentation around the hold. Periodically, it was removed so that it did not interfere with the steady burning of the flame. The bottom of the candle was set in a shallow dish which had a ring on its side connected through pulleys to a counterweight. As the candle burned away, the weight pushed it upward at a constant rate. The automata were operated from the dish at the bottom of the candle. No other candle clocks of this sophistication are known. (Source: History of Sciences in the Islamic World: http://home.swipnet.se/islam/articles/HistoryofSciences.htm.)

Next in Western candlemaking history, along came the whaling industry, and spermaceti was discovered and put to use for the next extraordinary candle — one that burned whiter, brighter, and odor-free. Now, that was unusual in a time when candles were generally made of tallow, which was difficult to render and nasty to work with. Lastly, after petroleum was discovered and taken out of its snug hiding place in the earth's depths, paraffin, a petroleum derivative, became the most unusual candle available. After that, with stearin, which hardened paraffin and made it opaque, most people thought candles had reached their pinnacle.