What’s in it: Powdered milk protein (casein), lime, and earth pigments; you mix it with water.
Great for: Brick, concrete, and raw wood; newer formulations go over painted surfaces; suitable for outdoor use if mixed with boiled linseed oil.
Magic properties: The casein bonds with the surface as the paint dries, so it’s tough and long lasting—50 years or more.
Caveats: Most types won’t work on drywall, painted wood, or metal; will show fingerprints and water spots if not sealed.
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