Types of Paint Strippers

Types of strippers: Strippers fall into three categories: caustic, solvent, and biochemical. There is no shortage of strippers to choose from. Many painters are loyal to one brand. If you’re not yet one of them, consult your dealer, quiz other painters, and experiment.

Here’s the range of answers I got when I asked several painters if they used chemical paint strippers:

  • “Never! Ever! It gives you brain damage!”
  • “Never! Well, except on concrete. Outdoors. And first, I get most of the paint off with a heat gun.”
  • “Occasionally, but only when I have to.”

After more conversations with painters and paint dealers, I found that many painters don’t understand how strippers work, or how to match a stripper to a job. Although many painters prefer to minimise their use of these chemicals, most painters must use them occasionally. So unless you’re a hard-core “Never! Ever!” painter, take the next few minutes to learn how to use strippers safely and productively.

Types of Strippers

Strippers fall into three categories: caustic, solvent, and biochemical.

Caustic strippers are water-based solutions with a pH of 13 to 14. Their active ingredient is lye, which may be either potassium hydroxide (known as caustic potash) or sodium hydroxide (caustic soda). When carrying out caustic paint stripping the lye reacts with the oily component of the paint film, turning it into soap. This reaction with the paint loosens it from the surface. The health risks of caustic strippers include skin burns and lung irritation.

Solvent strippers remove paint by dissolving or softening the bond between the film and substrate, causing the coating to bubble up. The most common solvent is methylene chloride (also called dichloromethane), but alcohol, toluene, acetone, and ketones are often also present.

Methylene chloride based strippers work very well. However, they pose more potent health risks than caustic strippers do. They temporarily reduce the blood’s capacity to carry oxygen and may cause permanent liver and kidney damage and cancer.

Another solvent is N-methyl-2-pyrrolidone (NMP), often used in combination with dibasic esters (DBE). Although these strippers are promoted as a safer alternative to methylene chloride, their health effects are not yet completely understood. According to the EPA, NMP causes skin swelling, irritation, and blisters. Dibasic esters cling nicely to vertical surfaces, but they work slowly and have been reported to fuzz the surface of the wood.

Yet another solvent system is a combination of alcohol, toluene, and methanol. This cocktail works quickly, but it evaporates quickly and is highly flammable. Breathing it can give you brain damage. The fact that it evaporates quickly reduces somewhat the volume of waste you must dispose of.

Biochemical-based stripping agents are another category. The solvents in them are derived from plants. Biochemical-based strippers may include terpenes, from pine or citrus; lactic acids, from corn sugars; dimethylsulfoxide (DMSO), from wood pulp and paper by-products; citric acid; and soy oil. Some of these materials can irritate your skin. In addition to the biochemical ingredients, most of these strippers contain NMP.

Although manufacturers of citrus-based products emphasise their suitability for commercial use, the paint stores in my town don’t report selling a lot of citrus-based strippers to professionals. If customers are concerned about odour, they may be happier if you use a citrus-based stripper. Remind them, though, that citrus-based strippers do contain harmful chemicals, and that the stripper will have to remain on the surface for a long time to work.

Strippers marketed as “safe” or “eco” don’t contain methylene chloride, but they may contain NMP, DBE, biochemical agents, or a combination.

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