The effect of alkali on oil based paints in the presence of moisture.  Mild attack causes the paint to soften and probably discolour.  In severe cases the paint may be completely destroyed.

Alkali in damp cement, concrete, lime plaster, asbestos or similar materials and contact with alkaline solutions will cause saponification of oil based paints.

When saponification has occurred, the surface must be stripped, washed and allowed to dry out completely before repainting.  If the paint is likely to be in contact with alkaline solutions, as in some industrial environments, non-saponifiable specialist coatings may be required.