Paints and varnishes can be difficult to remove from wood and other materials, and a wide number of solvents are available to help strip these types of finishes away. These solvents are usually derived from fossil fuels and can give off toxic fumes and carcinogenic compounds, so some people prefer to use more natural materials to remove paint and varnish. These strippers may not work as well, but they do have fewer toxins.
Citrus strippers are a popular alternative to regular solvents, and are often made using orange peels and similar castoffs from food processing. Citrus is an organic acid that is present in almost all living things, and does not contain dangerous solvent compounds. However, it may also stain some susceptible surface such as concrete, so it should be used with care.
While soybean oil is not acidic, it does have properties that allow it to loosen many normal paints, and is sold as a generic paint stripper. The oil must be allowed to seep down into the paint, where it slowly loosens the bonds of the paint from its material and allows the user to scrape the paint away. Soy oil does not work well on many types of urethane-based paints and varnishes, where a stronger solvent is needed.
While white spirit are derived from petroleum, they are far less toxic than many other types of solvents used for paint stripping. White spirit can cause eye and skin irritation, and is still very flammable, but can remove many varnishes that other eco-friendly alternatives may not be able to handle, with far fewer carcinogens or VOCs (volatile organic compounds).
For some types of paints, a heat gun can be used to removed layers of paint instead of a solvent. The heat soften the paint, loosens its bond and causes it to bubble up from the surface, making it easier to scrape away. However, heat guns can only be used with some types of paint, and are not effective at removing varnishes. They also may leave bits of paint that must be scrubbed off.
Types of Paints
How well the paint strippers work depends in large part on the paints themselves. If an eco-friendly paint was used on an object, it is more likely to come off more easily using a citric or soy remover than regular paint. Because "green" paints also avoid using petroleum-based compounds, the bonds they form tend to be weaker and more easily broken when stripping.