crease
Where a sheet material (e.g. paper) has been unintentionally bent over on itself. See also fold.
crazing
Describes a fine or microscopic network of cracks in a varnish or coating. Can cause the surface to appear cloudy due to changes in the way the surface reflects light.
craquelure
A network of fine cracks in a varnish or paint layer, which may be caused by several different deterioration mechanisms; e.g. different rates of drying between two layers, or the increasing brittleness of one layer relative to another.
crack
A narrow opening between two parts of a material that have split or become broken but may not be separated from each other. Usually used to describe breaks in more solid materials, such as stone, ceramic and wood. In plastics, refers to splits that follow the grain or direction of manufacture.
corrosion
Gradual deterioration of a solid (especially metals) due to chemical processes such as oxidation or the action of a chemical agent. Some corrosion products, like metal patinas, can be protective; others, like rust, can be harmful. Corrosion is often accelerated by contact with materials that generate acidic vapours – e.g. wood, plastics.
cockling
Wrinkling or puckering that occurs when paper, fabric, or any sheet of support material dries unevenly.
cleavage
The separation of paint from the ground layer of a painting, which may cause cracking, blistering and flaking.
channelling
In film, buckling of the emulsion layer due to shrinkage of the base layer.
chalking
In plastics, where the outer surface oxidises and becomes dry and powdery, reducing the surface lustre or sheen. The plastic will become more susceptible to ingrained soiling.
burn
Where a surface has been damaged by fire. Burned surfaces are usually black or brown in colour, friable and brittle. May be accompanied by soot and smoke damage, water damage and melting or softening. May also be used to describe damage caused by sunlight or chemical pollutants – e.g. light burn, mat burn.