Shoutout to the old timer who told me to soak my trowel in vinegar overnight
I laughed at him when he said it, figured a $4 bottle of vinegar was not gonna do anything my wire brush couldn't. Had a trowel caked with years of thin set that I was about ready to toss in the trash. Left it in a bucket of straight vinegar on a Tuesday and Wednesday morning the crud basically slid off with a rag. My helper asked why I was cussing at a bucket, and honestly I was just mad I waited 12 years to try it. What else am I sleeping on, because I've got a chalk line reel that's seen better days.
Buddy of mine had the same deal with his chalk line, metal body was rusted shut and he was gonna pitch it. Dropped the metal parts in vinegar for a day, wiped them down, and it clicked like new, though the line itself was still trash. Pull the reel apart, soak the rusty bits, and see what you get before you spend money on a new one.
Ha, I once soaked a shower head in vinegar and felt like a genius chemist, so you're not alone in the late-to-the-party club. The chalk line might just need a new reel more than a soak, but try the vinegar on the metal parts first. My own dumb move was waiting years to try it on grout, so at least we're both catching up.