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　　In the middle ages, oil lamps were very troublesome because they often needed to add oil, choose and adjust thread ends. Candles began to be used in parallel with oil lamps. At that time, the candles were made of cow or sheep fat, which was economical and concise, but the flame was yellow and there was smoke. By the 14th century, wax had replaced oil, and the early wax was bee wax. At that time, Saint Nicolas company of France made a candle twist composed of two cotton threads and one hemp thread, purified the grease and wax, and then put the twist into a vat filled with grease or wax, and hung the wax repeatedly. The production is very strict, to prevent counterfeiting, new wax and old wax to separate, sheep fat and cow fat can not be mixed together, line to ensure the satisfaction of cotton thread. At that time, there were very few candles. Bee wax was only used by the court, and ordinary people used grease candles.

　　In fact, modern candles began with the discovery of modern wax. In 1783, Carl Scheele, a Swedish chemist, discovered the mixture of olive oil and lead oxide while studying soap. In 1823, Michel Eugene Chevreul, a French chemist, further proved the discovery of wax making. In this way, modern candles began to develop in the mid-19th century. There are two differences between modern candles and old candles in the past: one is the material, the other is the thread. The modern thread is made up of several strands, avoiding the need to choose

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