Graffiti is a major, increasing danger to architectural heritage materials, generating also a negative social connotation. Apart from aesthetic aspects, interactions of graffiti with substrate, as well as cleaning procedures, threaten historical substance. Monuments made of stone, bricks and mortars are menaced by this problem because very often, porous natural materials were employed.

Two major kind of coatings are currently being used for protecting surfaces against graffiti: permanent and sacrificial. The first kind is suited for materials with low porosity, such as metals and concrete, but does not fit the requirements for porous ancient materials. The second is sometimes used in monuments, but it is not an appropriate solution, since removal procedures can damage substrates somewhat.