The technique seem to be good for materials like wax, see below for some photos of a wax candle for comparison.

技术似乎是好材料，如蜡、见下部分的蜡烛照片进行对比。

youdao

There is ample evidence that the poor do pay, often heavily, for inefficient, dirty energy say, from kerosene, candle wax and batteries.

ECONOMIST: A survey of Energy