This article will explain what types of paint can be used to paint brick. It will also present different scenarios that may happen that affect how the brick should be painted.
First, answer this question. Is the brick that is going to get painted on the exterior of a building or structure, or is it an interior wall or fireplace? The reason for this question is to determine whether exterior or interior paint is needed. In either case, the brick must be examined, because regardless of the paint that is to be used, the surface must be properly prepared. If the brick is unpainted, any loose or chalky brick must be removed with a wire brush. Then a quality oil-based primer should be applied. Use the appropriate primer for the conditions (interior or exterior use). If the the brick has been painted previously, assess the condition of the paint. If it shows no signs of distress (chipping, peeling or flaking), the brick must simply be dirt-free before it can be painted. If the paint is chipping, peeling or flaking, use a wire brush to remove the flakes or chips and prime any bare (unpainted) spots with a quality oil-based primer. Now your brick surface is ready to be painted.
Types of Paint (Composition)
Once prepared, there are two main types of paint that can be used, strictly from a standpoint of chemical composition. That is, whether it be interior or exterior paint, it is either water-based or oil-based. Simply put, water-based paints clean up with soap and water, generally have low odor, dry fairly quickly and do not yellow over time. Oil-based paints, while very durable and level (show very few brushstrokes), need mineral spirits to clean up brushes, take much longer to dry, take on a yellowish tinge over time and usually have a strong odor. From a quality perspective, both types are similar so long as a high quality paint is used. Most times, a water-based paint is the more accepted choice, as more states are enforcing strict environmental laws regarding oil-based paint.
Paint Subtypes (Water-based)
There are three types of water-based paint that can be used to paint brick once it is properly prepared. The first type, latex, should only be used to paint interior brick as it does not have the ability to flex or stretch like the next two types, which can be used either inside or outside. Those two types are acrylic and waterborne. Acrylic is becoming widely used because, as mentioned above, it can stretch along with weather conditions. The second type, waterborne paint, is a special technology meant to mimic the leveling (leaving few brush strokes) of oil-based paint. While it flexes like acrylic paint, it offers superior leveling to both latex and acrylic paint. All three types of paint dry quickly, though waterborne paints dry extremely fast. In summary, latex paint should only be used for interior brick, while acrylic and waterborne paints can be used on either interior or exterior brick.
A common myth is that water-based paints cannot be used to paint on top of old oil-based paints. In the past this was true, but as latex paints have improved in quality, their adhesion properties have improved. Still, the old paint must be scuffed in such a way for the water-based paint to adhere properly, either with sandpaper or a wire brush. Also, using a low-quality paint may negatively affect adhesion.
When painting interior brick, be sure to the area is well ventilated, whether you use oil-based paint or not. Be certain any previously painted surfaces were not painted with lead-based paint. Generally this paint would be at least 25 years old, as lead-based paint is no longer used because of health risks. There are testing kits available at many paint or home-improvement centers that will help determine if the old paint is lead-based. If this is the case, exercise extreme caution. Inhaling lead dust is very hazardous to your health. It is strongly advised that a professional be used in these cases, but there are approved breathing apparatuses that can be purchased that protect the wearer from breathing in the particles.