Q. We are restoring a 19th-century Victorian home with a painted brick exterior. The client wants to remove the six or more existing layers of paint, down to the natural brick. What is the best way to remove the paint without destroying the brick or mortar?
A.John Leeke, a preservation consultant from Portland, Maine, responds: These days, when working on any building built prior to 1979, you must comply with the EPA’s Renovation, Repair and Painting (RRP) rule. From a purely historical preservation perspective, however, the first step is to investigate the masonry to determine what type of bricks and mortar was used. Repressed bricks that are very square, with even sharp edges, and laid with narrow mortar joints, are usually fired hard and intended to hold up to the weather on their own. Some buildings were made of softer bricks with rounded edges; these softer brick were intended by the original builders to be painted. You wouldn’t want to leave this type of brickwork exposed with no paint, because the surface would absorb too much water, causing serious problems over the long term.
If the bricks need a coating, determine if the existing coating is still performing its intended function. If the bricks will have to be recoated for the good of the building, the owners will want to reconsider their decision to expose the bricks.
We do testing and development on every one of our paint-removal projects. We usually test at least three removal methods and materials, starting with the least aggressive methods. Mechanical methods like scraping, chipping, and dry blasting are more likely to damage the masonry than chemical methods.
Blasting methods that use any kind of grit usually damage the bricks by taking off the weather-resistant surface, exposing the more absorbent core of the brick. Blasting can also remove mortar, leading to the need for repointing. Even high-pressure blasting with plain water can blast out softer but perfectly good mortar. Although blasting must be approached with caution, we still sometimes test and use blasting methods, which can work well under certain conditions.
In recent years, our tests have usually led us into using wet/chemical methods with low-pressure washing. With these methods it is easier to control the hazard of lead-containing waste. Generally, solvent-type chemicals give better results than caustics, because un-neutralized caustics seep back out of the wall to damage paint coatings (even on adjacent woodwork).
To determine which removal methods and chemicals work best, we begin by testing small 1x1 foot patches. Then we select the best performing method, and try three or more variations on methods and materials on successively larger test panels.
Why is testing necessary? Because the conditions on these older buildings are so variable and unknown. On a recent project, a tradesperson who knew better skipped testing and development and signed a contract for a paint removal project on a masonry building. It turns out that back in the 1970s, an owner of the building (who was a chemist at a local industrial plant) painted the house with a special chemical-resistant epoxy coating. The removal took six times longer than expected and put the guy out of business.
