An oxidized condition of paint or aged asphalt that has lost its volatile oils due to exposure to sun and solar radiation, which is the ultimate result of the paint or asphalt’s limited tolerance to thermal expansion and contraction. Alligatoring is characterized by a coarse, checked pattern that results when a new paint coating slips over the old coating to the extent that the old coating can be seen through the fissures, producing a pattern of cracks resembling an alligator hide.
Crazing is the phenomenon that produces a network of fine cracks on the surface of a material, for example in a glaze layer. Crazing frequently precedes fracture in some glassy thermoplastic polymers. As it only takes place under tensile stress, the plane of the crazing corresponds to the stress direction. The effect is visibly distinguishable from other types of fine cracking because the crazing region has different refractive indices from surrounding material. Crazing occurs in regions of high hydrostatic tension, or in regions of very localized yielding, which leads to the formation of interpenetrating microvoids and small fibrils. If an applied tensile load is sufficient, these bridges elongate and break, causing the microvoids to grow and coalesce; as microvoids coalesce, cracks begin to form.