Buy a large candle, and use a mechanical pencil with no lead in it to engrave a message.

买一支大蜡烛，然后用一支没有装铅芯的自动铅笔在上面雕刻一些特别的标语。

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The rain has started and the sky is turning the color of the lead in a number 2 pencil.

FORBES: Cars and Hurricanes

The poem "O, I won't lead a homely life" was written in pencil below the score, though to an old folk tune.

BBC: Thomas Hardy's musical manuscript poem sold for ?5,000

An analogy: think of a pencil, where the lead in the middle is the cellulose fiber, surrounded by unwanted lignin and hemicellulose.

FORBES: Ethanol