"A Japanese student of ninja history who handed in a blank paper was given top marks - after her professor realised the essay was written in invisible ink.
Eimi Haga followed the ninja technique of "aburidashi", spending hours soaking and crushing soybeans to make the ink.
The words appeared when her professor heated the paper over his gas stove."
@sohkamyung I remember doing this as a kid, but I was using lemon juice.
@loke Me too. 🙂
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