Decorating and painting concrete blocks can turn an average, boring-looking wall or garden border into a work of art. Concrete block painters have the option of smooth or split-face exterior concrete block surfaces. Smooth concrete blocks remain the easiest concrete blocks to decorate and paint. When it comes to the style and design of artwork on the concrete block, the only limit is the individual's imagination.
Use a stiff-bristled scrub brush to clean the smooth concrete blocks. Add a few drops of dish soap to a bucket of lukewarm water. Dip the scrub brush into the soap mixture and scrub each concrete block to remove any grime, dust or dirt. Scrape any leftover paint residue off with a putty-knife.
Apply an acid wash to the concrete blocks to remove the white powder layer not removed by soap and water. Purchase acidic masonry cleaner online or in home improvement stores. Wear gloves and wash the concrete blocks with the acidic masonry cleaner according to directions. Different brand manufacturers will have varying application instructions. Allow concrete blocks to thoroughly dry before continuing.
Rent a commercial pressure washer from an equipment rental store. Spray the concrete blocks with a 15 degree pressure washer tip, at least 12 inches away from the block surface. Move the spray of the pressure washer back and forth over the concrete blocks in a horizontal pattern. Allow the concrete blocks to completely dry before proceeding.
Dip a paintbrush in a can of acrylic block fill primer and layer a liberal amount onto the concrete blocks. Smooth the primer over the entire concrete block surface so all of the surface pores are filled in and smooth. Allow the concrete blocks to dry.
Buy decorative stencil patterns from a craft store, and use the painter's tape to stick the stencil to the concrete block. Arrange the stencil on the concrete block in any desired pattern. Use the stencils to add various patterns on the concrete blocks. Use small brushes to apply acrylic paint one colour at a time. Allow the paint to dry after each application coat.
Remove the stencil and painter's tape from the concrete blocks. Spray two coats of clear spray varnish onto the concrete blocks. Allow each coat to dry before spraying on the next coat.
Do not use too much paint when using stencils. Start with a small amount of paint on the brush to stop the paint bleeding under the stencil.