How to Stain Concrete Block Walls
Concrete block walls are an economical choice, but often do not come with many color options. This can all be solved by using a concrete stain, to give the wall more color and depth. If desired, various faux finishes can be applied, and multiple stain colors can be mixed, to give you a unique finish. Most large home improvement centers rent out paint sprayers and pressure washers, if you do not have personal access. Though these items are not completely necessary, they make the job much simpler, and provide a more uniform finish. Staining concrete is not a difficult job, but it does mean you will be working with multiple chemical products. Always wear clothes which fully cover, and can get stained. Wear safety masks and goggles, and be cautions about children and pets.
Step 1 - Cleaning
Before any stain is applied, the concrete wall must be thoroughly cleaned. Just as stain brings out the grain in wood, it will magnify any imperfection, grit, grime or discoloration. These marks will then be permanently stuck on the concrete. Use the pressure washer to blast away any grime from the wall. Allow the wall to thoroughly dry.
Step 2 - Etching Solution
Some concrete block has been treated with smooth, water repelling chemicals. These blocks will not absorb the stain enough for the color to take. The concrete block should readily absorb water, and have a rough abraded surface. If in doubt at all, use the concrete etching solution to break up the first layer of the concrete, and allow it to absorb the stain. Mix the etching solution as the manufacturer instructs, and allow it to sit on the concrete for at least 1 hour. Be careful when rinsing the solution off, as it might adversely affect plants. Allow to dry for 24 hours before staining.
Step 3 - Staining
Cover all surrounding spaces which you do not want to stain with at least 18 inches of sheet plastic and duct tape. The stain is going to be sprayed on, so the tape needs to be able to hold securely. Purchase enough stain to cover the area at least twice. Spray the stain in a circular pattern, beginning from the upper corner and across the space. Spray only until the concrete begins to absorb the stain. To avoid drips in the stain or blotchiness, apply multiple light coats.
Step 4 - Sealing
Dissolve a solution of 2 cups baking soda to 1 gallon of water, and pour over the stained wall. The solution will neutralize the stain. Rinse with a garden hose, being careful not to overly blast the unsealed concrete. Once allowed to dry for 24 hours, use the paint roller to apply a concrete sealant, and fully adhere the stain. Use the concrete sealant according to the manufacturer's instructions, but be sure to apply 2 coats. Do not remove the plastic, until after then sealant has adequately dried.