Polyurethane Stripping Techniques for Wood

Polyurethane needs to be completely removed for a successful refinishing project.

Stripping polyurethane is one of the first and most important steps in any wood refinishing project. Whether refinishing furniture, the floor or other wood surfaces, polyurethane must be completely removed before a new coat of paint, stain or other coating can be properly applied. There are several techniques for removing polyurethane, and experimentation is often required in order to find the right solution for any given project.

Sanding

Power sanders are designed for a variety of specific jobs.

Nearly every refinishing project requires sanding. Whether or not other techniques are also used, sanding helps not only to remove polyurethane and other coatings, but also to achieve a smooth surface for the application of new coatings. Tools used for sanding range from basic hand tools to power tools designed for very specific purposes. Large belt sanders, for example, are used on floors, while smaller tools are available for use in corners and small areas. Lower-grit, or rougher sandpaper is used first to remove the polyurethane and then gradually stepped up to higher-grit, or smoother sandpaper to achieve an even finish. Polyurethane can often be completely removed with sanding only, however, utilizing other techniques, such as those described below, speeds the process.

Heat

Applying heat breaks down polyurethane so it can be removed from the wood.

Applying heat can be very useful in removing polyurethane from wood. Typically, a heat gun is used to raise the temperature of the polyurethane to a point where it begins to break down and can be removed with a metal scraper or other tool. When using this method, care should be taken not to overheat or scorch the wood surface.

Chemical Strippers

Proper precautions should be taken when using chemical strippers.

Chemical strippers remove polyurethane from wood through chemical reactions that weaken the bond between the polyurethane and the wood surface. Available in liquid or paste forms, chemical strippers are left on the wood surface for a predetermined amount of time before being scraped off along with all or most of the polyurethane. The wood surface is then cleaned with a solvent to remove remnants of the active chemicals. Check the label of the stripper you are using for cure time and recommended solvents. All safety and health warnings should also be read carefully, as chemical strippers can be dangerous if exposed to skin or if their fumes are inhaled.

Non-Toxic Strippers

Non-toxic and non-chemical strippers take longer, but are more easily used indoors.

A variety of non-chemical and non-toxic strippers are also available. These typically have longer cure times, but do not carry as many health and safety warnings as chemical strippers, and therefore can be used more easily indoors or in small spaces. The process for using these strippers is similar, if longer, to that of chemical strippers -- apply, allow to cure, remove with scraper. As a last step, the wood surface is usually cleaned with either water, a solvent or a neutralizing liquid specially designed for that stripper.

References

• Paint Pro: Paint Strippers, Types of Strippers
• WoodZone.com: Sandpaper 101
• Ace Hardware: Removing Paint and Varnish