The homebrew crowd has a word for dried-on bits---beerstone. I e heard you cant soak it off. But the jars are glass, so you can use harsh chemicals if needed. I suggest soaking w water and deturgent first. Then, acid, rinse, base, rinse rinse rinse. Ypu can use acetic acid and lye, but rinse between. For really strong acid or base, dry jars before immersing.