LIBERTY chalk paints are liquid and produced and packaged in the EU. They are applied to any surface. You don't need for the surface to undergo any treatment. The colors can be mixed together. They are water soluble. Each package of 200ml can cover an area of 3 to 3.5 sq.m. about, while the packaging of the liter can cover about 14 sq.m. Shake the package well before each use.