Foam residue on old brick

[Fake_Seej]

While helping a coworker with his 1970s brick home in Denver, we removed the old door frame and discovered expansion foam and paint residue underneath. Tried acetone, diluted acid, and a wire brush but the foam is stubborn and the brushing is leaving a gray tint. The brick is red and textured, so we're trying not to damage the face. I've read that exposing it to sunlight can help break it down but this wall faces north. Would a heat gun or a soft scraper be worth trying before we call in a mason?

 

[BanditVarkas]

Forget the sunlight trick, north-facing wall isn't gonna see enough UV to matter. Heat gun and a sharp scraper is about as good as it gets without chewing the brick up. Foam's nasty once it's cured... sometimes you just have to accept it won't look factory new again.

 

[TheStoneBuilder]

While helping a coworker with his 1970s brick home in Denver, we removed the old door frame and discovered expansion foam and paint residue underneath. Tried acetone, diluted acid, and a wire brush but the foam is stubborn and the brushing is leaving a gray tint. The brick is red and textured, so we're trying not to damage the face. I've read that exposing it to sunlight can help break it down but this wall faces north. Would a heat gun or a soft scraper be worth trying before we call in a mason?

Foam can really be stubborn, but first you have to stop with the wire brush. That gray tint is a sign you're damaging the face of the brick, which you definitely don't want to do. You're basically grinding away the harder, fired surface, exposing the softer clay underneath. This can lead to spalling down the road. I'd also go with @BanditVarkas's idea and use a heat gun and plastic scraper or a stiff nylon brush. A metal scraper might scratch the brick, so be careful. Once it's soft, you can usually scrape or peel off most of the gunk. For any remaining residue, you can use a urethane foam remover. It's specifically made for this kind of cleanup and won't damage the brick like harsh acids or wire brushing. Just be sure to test it on an inconspicuous spot first.

 

[Fake_Seej]

A real eye opener. It accounts for the gray stain we're seeing. We will stop using the wire brush immediately. Will try a heat gun with a plastic scraper this weekend. Regarding the urethane foam remover, is there a specific brand you trust for older brick?

 

[TheStoneBuilder]

Good call on stopping with the wire brush! For a urethane foam remover, check out Foam Eater, Krud Kutter, or Sika Remover-208. They're designed to break down the foam without damaging the masonry. Just be sure to test it on a small, hidden area first to check for any discoloration. Good luck and let us know how it goes!

 

[vladimir56]

Foam can really be stubborn, but first you have to stop with the wire brush. That gray tint is a sign you're damaging the face of the brick, which you definitely don't want to do. You're basically grinding away the harder, fired surface, exposing the softer clay underneath. This can lead to spalling down the road. I'd also go with @BanditVarkas's idea and use a heat gun and plastic scraper or a stiff nylon brush. A metal scraper might scratch the brick, so be careful. Once it's soft, you can usually scrape or peel off most of the gunk. For any remaining residue, you can use a urethane foam remover. It's specifically made for this kind of cleanup and won't damage the brick like harsh acids or wire brushing. Just be sure to test it on an inconspicuous spot first.

I was using a wire brush on some old expansion foam around my basement window and noticed the brick turning dull. Do you know if the urethane remover works on foam that's been baked by the sun for years, or should I try the heat gun first to loosen it up?

 

[Fake_Seej]

Thanks @TheStoneBuilder for the specific brand recos.

The plan is to grab some Foam Eater and try it on a hidden test patch this weekend with a plastic scraper, just as you suggested. I definitely won't be skipping that step, as I now understand how much older brick can vary in quality.

I'll report back with the results in a week or so for the benefit of the community. Thanks, everyone!