Polyurethane foam is more common than you may realize. It's used for support in your mattresses, chairs, car seats and for insulation in your walls. It's also found in sponges, medical dressings, large filters and soundproofing systems. Polyurethane plastic comes in a flexible foam form that can be applied with a spray can, which makes it easy to use for DIY projects. It is, however, irritatingly difficult to remove. Not only is the material stubborn and resistant, if removed the wrong way it can cause permanent wall damage. To remove unwanted foam, you'll need various tools and some elbow grease as you try scraping, sawing, prying and dissolving.
Scrape, Saw, Pry
First, check whether the foam has cured (dried). A noncured material may dissolve on its own over time – no chemicals or blades necessary. But, if the foam has cured, it's time to get out the tools. You can use a stiff-bristled or power wire brush to scrape off the foam and then rinse with water to remove any residue. For stubborn spots, you can use a reciprocating saw. Avoid cutting at a 90-degree angle so as not to ruin your wall, and steer clear of pipes and electrical lines. You can also go the prying route, using old claw hammers and pry bars. Older versions of these tools are preferable because the blunt edges will help avoid damaging the wall. Other tools that can be used for removing Polyurethane foam include a long-handled serrated trowel, a drywall saw and a wide-blade putty knife.
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Acetone, Not H2O
Use acetone, which is found in nail polish remover, to clean off uncured wall foam. But, first, test it on a more discreet section of the wall to make sure it won't do any damage. Moreover, avoid cleaning with soap and water, as the moisture will make the foam cure and worsen the situation.
Lacquer thinner, which can be purchased at home improvement stores and online, should do the trick when it comes to removing cured wall foam insulation. Carefully follow the instructions provided on the label.
Don't, under any circumstances, apply heat to remove foam insulation. The foam contains many toxins that can be released into the air if heat is applied. When in doubt, call for professional help. It's better to err on the side of caution then cause damage to your wall or, worse, to your health.