A hard resin that protected whatever it covered from decay.

一种能保护覆盖物不受风化的牢固树脂。

The operation, which lasted for over four hours, proved to be very difficult because of the hard resin which covered the skin.

手术持续了4个多小时，非常难做，因为皮肤上覆盖着一层硬硬的树脂。