Made of synthetic resins, polyurethane varnish is favoured for its abrasion resistance and longevity. Polyurethane varnish is often used to finish wooden decks, floors and kitchen cabinets. Although polyurethane provides a tough finish, this transparent varnish eventually wears off and requires removal. Inadvertently spilling or transferring polyurethane varnish onto undesired surfaces also calls for the varnish's removal. Since polyurethane is so durable, the varnish requires chemical-based strippers to penetrate and dissolve it from surfaces. Carefully dissolve polyurethane varnish using basic techniques.
Protect yourself from the chemical-based stripper by donning chemical-resistant gloves and eye protection. Provide plenty of ventilation within the workspace to reduce harmful vapours.
Cover exposed surfaces surrounding the varnished item with heavy-duty dust sheets to reduce clean-up time and effort.
Dab methylene chloride-based stripper heavily over the polyurethane varnish using a disposable paintbrush. Follow the specific stripper manufacturer's directions precisely and only focus on a manageable portion of the varnish, such as a 1-by-1-foot section of the varnished surface.
Let the methylene chloride-based stripper dissolve the polyurethane varnish for the dwell period recommended on the stripper's label. Don't rush the process -- removing the stripper too soon may cause unfavourable results.
Scrape the dissolved polyurethane varnish off the surface using a thin-bladed putty knife with rounded edges. Remove as much polyurethane as possible.
Continue stripping the remaining 1-by-1-foot sections of the varnished surface until no more polyurethane varnish remains. Follow the previous stripping techniques and reapply the methylene chloride-based stripper if necessary.
Saturate an old cloth liberally with white spirit. Wipe the stripped surface with the soaked rag to remove the methylene chloride-based stripper. Clean the stripped surface thoroughly with white spirit.
Let the stripped surface air-dry for 24 hours.
Remove the softened varnish from hard-to-reach crevices using a wire brush.
Methylene chloride-based strippers are caustic and toxic; keep kids and pets away from them.