Stress whitening is a name for an optical effect, that is caused by microscopic cracks in the material, when plastic (polymere) is highly stressed or overused during processing or deformation. Thus, the properties at this point change (cracks, refraction at the cracks) and the plastic appears brighter.

Distinctive features

Whitening: milky white or white-gray discoloration on the plastic's surface.

To avoid this defect that is especially noticeable on dark plastics, smoothing stations are used for edgebanders.