Rarely but it does happen I have polishes that harden or get chunky/clumpy. Well a striper "went bad" before I could even use it! I scraped out clumps (the more chunks removed it will be easier to clean with less acetone to waste). I scraped out the big clumps with a plastic cuticle pushing stick and a dotting tool. In went the acetone, I shook it for a while then poured out the excess. I cleaned the metal ball on a cotton ball. I didn't clean it thoroughly but enough to keep this striper brush and bottle around to use and reclean for other colors I like.