Development of Hairline Cracks in Oil Paintings
Why do oil paintings develop hairline cracks and acrylic paintings do not?
This is directly related to the binders used in oil and acrylic paint. Oil paint binder (linseed oil) dries to an inflexible weak film. As temperature and humidity conditions change and the substrate expands and contracts, this inflexible film can crack. In addition, linseed oil dries very slowly. If the lower paint layers contain more linseed oil than paint applied on top, the top layers will tend to dry sooner. This may cause cracks to develop.
Acrylic paint remains flexible, which prevents the paint film from cracking. Acrylic paint binder (acrylic polymer emulsion) dries to a flexible paint film because the molecules interlock. They “move” with the substrate (canvas) during expansion and contraction due to heat or cold and humidity.
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