Modern paints are engineered to adhere tightly to surfaces, resist moisture and chemicals, and stand up to extreme temperatures. That’s a lot of value in a gallon of paint. These properties also create hassles when you want to remove old paint. We’ve assembled our top five methods for removing old paint. While some methods may be easier than other ones, they all require a little elbow grease.
Sanding and Scraping
A fairly low-tech approach is to perform hand sanding and/or scraping. You can make it a little easier by using a power sander, but you have to careful not to remove too much substrate in the process. These mechanical methods remove paint by physically breaking the chemical bonds between the paint and substrate. Scraping might be better suited for curved surfaces, and some scrapers have special profiles for common shapes. Sandpaper works better on flat surfaces. You can use wet/dry sandpaper with water or solvent to keep the dust down. Wear a filter mask when you use a power sander.
If you want to remove paint from exterior wood surfaces, a pressure washer can work quickly without creating dust. Like other mechanical methods, the pressurized water physically disrupts the paint’s adhesion. Furthermore, the water can help re-dissolve some components of water-based paints, reducing the required pressure needed to remove the paint. Use the manufacturer’s recommendations for psi and nozzle profile — too much pressure can damage the wood. Prepare for substantial runoff to ensure you don’t flood your spouse’s prized rose bed.
Akin to pressure washing on steroids, power washing is available for removing paint from metal surfaces. Power washing machines accept detergents to augment the pressurized water, which may be heated to help the detergent penetrate deep into the paint layers and soften the old paint. Detergents reduce surface tension, which helps to break the paint’s adhesion, whether water- or oil-based.
Tools such as hot air guns and electric elements can help melt or soften paint prior to scraping, often with nothing sharper than a putty knife. We don’t recommend you use open flame tools because of the potential fire hazard. Furthermore, even non-flame tools can start a fire or cause scorching if used improperly, so make sure you follow the instructions accompanying the tool.
These include caustic pastes and semi-paste solvents:
- Caustics usually contain lye and work by breaking down organic molecules in the paint responsible for its adhesion properties. If left on wood for too long, it can decompose cellulose fibers, causing darkening or raising grain. You have to neutralize caustics with a mild acid wash. Caustics work well on concrete, masonry and ironwork, but should not be used on aluminum because of unwanted chemical reactions. Safety precautions are required, including eye and skin protection.
- Solvents come in several varieties and are quite versatile. Methyl chloride (MC) solvents have small molecules that penetrate deep into paint layers. As the solvent begins to evaporate, it causes the paint layers to wrinkle and loosen. MC creates unhealthy vapors and requires careful application. N-methyl pyrrolidone (NMP) is a larger molecule, making it somewhat safer, but also slower. Like MC, NMP breaks the chemical bonds between the paint and substrate, but is ineffective on baked-on or polyester coatings. Newer solvents, containing non-toxic chemicals such as soy esters and citrus compounds, are safer to use and can be quite effective. Special strippers can be used on lead paint to make the lead insoluble, reducing hazardous leaching.
PennCoat, Inc. has been providing industrial painting, commercial painting, epoxy flooring, and polished concrete services for nearly 30 years. Our experienced installers are trained and equipped with the proper knowledge and tools to ensure that every installation is installed efficiently and safely. PennCoat, Inc. provides service to Pennsylvania, New Jersey, Maryland, and Delaware. And we cover York, Lancaster, Philadelphia, Chester, Montgomery, Baltimore, Harrisburg, Dauphin, Bucks, Berks, and other counties in the surrounding area.