Why does leather get hardened after tanning?

Explanation

### Step-by-Step Solution:

1. **Understanding Leather Composition**:
- Leather is derived from animal hides, which are primarily composed of collagen, a protein that exists in a colloidal form. This colloidal nature means that the particles in the hide are dispersed in a medium, giving it a soft and flexible texture.

2. **Introduction to Tanning**:
- Tanning is a chemical process that transforms the raw animal hide into leather. This process involves the application of tanning agents, such as tannins, which are typically derived from plant sources.

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