Caustic, solvent and biochemical strippers are the three types of paint strippers. Caustic strippers are water-based solutions with a PH of either 13 or 14.
Caustic stripper's active ingredient is lye that is either caustic potash or caustic soda. The paint removers must be neutralized; the new finish fails otherwise prematurely. Caution must be taken when using caustic strippers due to several side effects and health risks. Solvent paint removers take away paint through dissolving or softening the bond between the film and substrate, making the coating bubble up. Methylene chloride is a common solvent, but alcohol, toluene, acetone and ketones also exist. Methylene chloride-based strippers pose more health risks than caustic strippers. They reduce the capacity of blood to carry oxygen and can cause permanent liver and kidney damage and cancer.
Biochemical removers contain solvents obtained from plants. They include terpenes from pine, lactic acids from corn sugars, citric acid and soy oil. Some of these strippers can cause skin irritation. The principle of paint removers is penetration of the paint film by molecules of the active ingredient, resulting in swelling. Internal strains caused by the increase in volume, which together with the weakening of the layers adhesion to the underlying surface, result in the separation of the layer of the paint from the substrate.