It has been valued for its strength, durability, and insulation properties. It can be cut, cleft, or sculpted to shape as required, and the variety of natural stone types, textures, and colors provide an exceptionally versatile range of building materials. The porosity and makeup of most stone does, however, leave it prone to certain types of damage if unsealed.
Staining is the most common form of damage. It is the result of oils or other liquids penetrate deeply into the capillary channels and deposit material that is effectively impossible to remove without destroying the stone.
Salt Attack occurs when salts dissolved in water are carried into the stone.
The two commonest effects are efflorescence and spalling. Salts that expand on crystallization in capillary gaps can cause surface spalling.
Sealing helps protect the surface for longer.