If there's one thing I've learned the hard way while sealing up gaps around the shop, it's that polyurethane expanding foam (like Great Stuff) is an absolute nightmare once it cures. Last weekend, I managed to get a significant amount on my favorite pair of pliers and the edge of the workbench.
While the foam is still wet, standard acetone will melt it right off. But once it cures, it becomes impervious to almost everything. Water does nothing. Soap does nothing. Scraping it with a razor blade usually just ends up scratching the underlying surface.
After ruining a good shirt trying to mechanically peel it off, I started looking into chemical solvents that actually break down the cured molecular structure without melting the plastic handles of my tools. I found a very effective method involving specific commercial solvents and proper dwell times. If you are dealing with a similar mess, I highly recommend reading this breakdown on how to remove cured expanding foam. It covers the exact chemical options that work, including using products like Goof Off Professional and taking a multi-step approach to soften the foam first.
Lesson learned: Always wear disposable nitrile gloves when touching that spray can.