Mottle

Mottle or mottling is the appearance of uneven spots. It is commonly used to describe plants or the skin of animals. In plants, mottling usually consists of yellowish spots on plants, and is usually a sign of disease or malnutrition. Many plant viruses cause mottling, some examples being:

• Tobacco vein mottling virus
• Bean pod mottle virus

Mottling is sometimes used to describe uneven discolored patches on the skin of humans as a result of cutaneous ischemia (lowered blood flow to the surfaces of the skin) or Herpes zoster infections. In animals, mottling may be a sign of disease, but may also be a hereditary trait, such as seen with the champagne and leopard complex genes in horses.

Mottles can also refer to discoloration in processed food, such as butter.

In geology, mottled refers to a patchy/blotch texture of alteration or interbedding, commonly found in limestone and commonly caused by bioturbation.

Mottling can also refer to an undesirable defect which can occur with effect coatings, most obvious on light metallic finishes. The total color impression shows irregular areas of lightness variations. These "patches" are usually visually evaluated, described as a mottling effect. Some also feel that it reminds them of clouds. This effect is especially noticeable on large body panels. It can be caused by the coating formulation, as well as variations in the application process. For example, disorientation of the metallic flakes or film thickness variations of the basecoat can lead to various mottle sizes resulting in a non-uniform appearance. The visual perception of mottling is dependent on the viewing distance: Large mottles can be seen in far distance evaluation, while small mottles are more noticeable in close up evaluation. The visual evaluation of mottling is very subjective, as it depends on the illumination conditions, the observing distance and the viewing angle.