It is this tannin which makes leather durable and soft.

鞣酸让皮革更加柔软，更耐用。

It takes years for a skeleton to vanish, but the shoes treated with tannic acid—they won't eat them.

骸几年才能消失，但是用鞣酸处理过的鞋子——海水无法吞噬们。

During the summer the bark is peeled from the trees and taken to factories where the tannin is taken out.

在夏天，我们会从树上削树皮，之后进入取鞣酸。

Turns out, it was made from the tannic acid of gall nuts.

原来，是用没食子（五倍子）中的鞣酸制成的。

The water draws out of this bark a substance known as tannin; and the tannin changes the soft, jelly-like skins into tough, strong leather.

在水的作用下, 树皮能够分泌一种名叫鞣酸的物质, 而就可以把凝胶一般柔软的毛皮变成结实、牢固的皮革。