Hierarchy classification:

1. top of the aat hierarchies
2. Materials Facet
3. Materials (hierarchy name)
4. materials (substances)
5. [materials by form]
6. [materials by chemical form]
7. compounds (materials)
8. organic compounds

Anotations

Scope note:

A colorless crystalline organic compound that is a product of protein metabolism in mammals. Urea can break hydrogen bonds and destabilize collagen. In conservation practice, this interaction reduces hardness and deformation in parchment, leather, and related materials.