Faux painting is a popular technique for painting walls, pottery, statues and columns. It is designed to look like natural rock, such as marble and slate, without the cost and difficulty of using real minerals. Many techniques are used to create the look of real stone, including sponges, artist brushes and feathers. Slate is very similar to marble when faux painting because it has small color differentiations made by using a main color and a second color, then a detail color that is usually white. Slate comes in many colors, and once you find a sample of the colored slate you are trying to reproduce, you can manipulate the paint to look like the real thing.
Apply your main paint color to the entire area you wish to cover, using a medium-sized paintbrush, paint roller or sponge. This should be the darker of the two colors. Let dry.
Dip a sponge into the second, lighter shade. Dab the sponge onto a spare cloth to remove most of the paint. It should be the same color as your main color, but a lighter shade. For example, if doing a dark green slate, use a lighter, sage green as the second color. Lightly dab the sponge onto the painted surface. Use a second dry sponge to dab the wall, removing any excess paint. You want the second color to be very indistinct.
Mix 1 part white paint with 4 parts glaze. Glaze gives the paint a translucent look, allowing for the detail in the faux-slate look.
Dip the small brush into the glaze mixture and wipe off any excess. Create the "veins" or lines found in slate. Slate can have thin, straight lines or thin veins running through it -- use your sample as a reference and follow the markings. Use the angle brush to create fine lines with extending branches for veins.
Dip one side of the feather into the mixture and wipe off any excess. Wipe the feather randomly across the painted surface, creating a weathered look. You can remove any excess paint with the sponge or a towel. Allow the surface to dry thoroughly.