"They used green vitriol water to draw the desired shape on yellow paper in advance, then let it dry, so from the outside, it looks no different from ordinary yellow paper. The reason they used tea to spray is because the tannins in the tea react with ferrous ions in green vitriol to quickly produce ferric tannate, which oxidizes to turn blue-black. This is the secret of revealing the hidden image; anyone who has attended a chemistry class would understand this principle."
As the former literature champion, plus two years at the Medical University.
Such a simple chemical reaction is naturally no trouble for Lin Yifan.
After his explanation, although the villagers were puzzled and didn't understand.
But clearly, Lin Yifan achieved it, and it wasn't some divine trick.
"Then what is this demon-slaying thing?"
Shen Shiyao still didn't fully grasp it.
How can a wooden sword kill ghosts?
Lin Yifan cast a sharp gaze at the two conmen across, who were sweating cold sweat.
