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There's some kind of orange yellowish looking substance that forms into tiny bubbles (it looks sticky, but I haven't touched it). It seems to be on my floor joists and wall studs. The house is from the 1960s. Is this something to worry about? Termites?

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You are looking at tree sap. It's harmless. It's dried out so if it's gonna cause you to lose sleep at night, just scrape it off with a chisel.

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    Sap is also known as pitch, at least for the softwoods that house framing is made from normally. – Ecnerwal Jan 2 at 2:22
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That is tree sap. My Grandfather would call it Pitch. Pitch will clean very nicely with kerosene or a naptha product such as coleman fuel. It looks like it is dried out and it should not hurt anything unless you are trying to paint over it.

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    If trying to paint over it you need "knotting"... at least that's what it's called in the UK, elsewhere it might be different. – Mark Morgan Lloyd Jan 2 at 9:14
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    Of course one should be careful with kerosene/naphtha, due to its flammability and toxicity. Be sure to ventilate the area until the stuff has dried. – Hot Licks Jan 2 at 19:06
  • The sap is also quite flammable, so scraping it off is advised, and better than adding flammable to it. – WGroleau Jan 3 at 7:10
  • My father told me that genuine, real shellac will seal knots better than any amount of primer, oil based or latex paint. I’ve not had occasion to try this but I have learned that my father’s advice, based on his 80 years of life experience, has been correct far more often than not. And that took me just 50 years to realize. Curious if anyone has used shellac to seal knots before painting over. – pndfam05 Jan 9 at 16:59

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