Milk Paint has been around for thousands of years, with the roots as far back as 6,000 years ago when it was used for cave paintings. It is now gaining recognition as a biodegradable, green product. Milk paint is made from milk and crushed, natural pigments, and it is used for walls, furniture, and even art. It is very durable, as it hardens with age. But, beware, there are companies who market "milk paints" which are not natural and contain harmful chemicals.
The two best known, true milk paint companies (both on the east coast) on the market sell the paint dry and you simply mix it with water. This is also a more efficient way to ship, since the water would make it much heavier and require more fuel to transport. Both companies sell about 20 colors that can be lightened into various shades and mixed to create an infinite palette. Powder is sold in pint, quart, and gallon amounts, with a gallon price being around $45.
The Milk Paint company in Groton, MA has dealers in almost every state across the country or you can order directly from their site. They also have a great gallery of products finished with milk paint. The other company is in PA and is called the Real Milk Paint company.