Concrete stain transforms a cold, grey patio slab into a warm oasis. It also provides translucent colour that often mimics the designs and patterns of natural stone, but any stains or imperfections in the concrete slab will be accentuated by the stain. You can stain old concrete as well as new, but the concrete must be fully cured and in good condition before staining.
Clean the surface of the concrete with soapy water and a scrub brush. Thoroughly rinse the soap from the concrete and allow it to dry. Apply a concentrated concrete stain remover to any stained areas until the stains are removed. Stains and imperfections in the concrete surface will show through the coloured concrete stain. If the concrete is sealed, strip the sealant from the surface with a concrete stripper so that the stain can penetrate the surface. Make sure that water does not bead on the surface of the patio before attempting to stain the concrete.
Protect the areas surrounding the concrete patio with plastic. Cover plants, walls, steps and any other areas that you do not want damaged by the acid and acid vapours of the concrete stain. Tape the plastic to the outside edge of the patio, either on the side of the concrete or in the yard surrounding the patio. Any area under the plastic or tape will not receive stain, so do not tape the plastic to the top edge of the patio.
Put on protective clothing including safety glasses, gloves, boots and a respiratory mask.
Shake or stir the concrete stain container to mix the contents and fill a paint sprayer with concrete stain. Use a sprayer with no metal parts that is safe to use with acidic products.
Spray the concrete in circular motions, working in small areas. Fully wet the area, but do not allow the stain to puddle or pool on the surface.
Follow the spray with a stiff scrub brush, moving the brush in circular motions to force the stain into the surface of the concrete. Work quickly and do not allow the stain to dry before scrubbing with a stiff brush.
Spray the concrete with a second coat of stain. Keep the sprayer moving and apply an even coat of stain.
Continue spraying layers of stain until you achieve the colour and finish you desire. Allow the stain to dry for 24 hours.
Neutralise the acidic stain with a commercial neutralising solution, baking soda powder or with a solution of baking soda and water. Spray the neutraliser, or sprinkle baking soda, on the surface, scrub with a brush and rinse until no colour releases from the concrete when wiped with a white towel.
Apply concrete sealer to the surface of the concrete with a paint roller or sprayer. Allow to dry a full 48 hours, or the time recommended by the product's manufacturer.
If possible, allow new concrete to cure 30 days before applying concrete stain. Uncured concrete has a higher water concentration than older concrete, which will affect the final colour of the stain and possibly cause spotty colour variations on the surface. When using a concrete stain that is not acidic, an acidic primer must be applied before staining the concrete. Apply the acid with a paint sprayer, allow the primer to dry according to the manufacturer's recommendations and then neutralise the acid with a baking soda and water solution. Rinse the neutraliser from the surface and then apply the concrete stain. Concrete stain does not provide a smooth, uniform finish. Slight variations in the final colour and patterns in the finished surface are normal effects of concrete stain.