Its happened to all of us at one time or another. Either you danced with your coven around a roaring fire as incense smoke rose from your cauldron and a gentle mist filled the night air, or your latest potion seems more fit for unclogging your toilet than making the cute box boy down at the grocery store fall in love with you, so you wash it out and leave it in the sink to drip dry.
No matter how it happened the end result is the same. You have [dum, Dum, DUMMMM] ....crusty cauldron...and now all the other witches down at the covenstead are going to make fun of you. Who does Barbie Witch think she is anyway with her perfect hair and flawless skin? Who died and made her the High Priestess of your Easy-Bake Coven? You've had it up to your pointy little hat with her. You'll show her, you'll show her good! Right? But how?
Well don't fret Wicca Babies, your Uncle Dino has the cure for what ails ya! Take your cauldron outside to a sandy area of your yard. DO NOT do this near any dry grass or leaves. Go to the beach if you have to. Lay the cauldron on the ground and pour some lighter fluid or a bit of rubbing alcohol over it. Strike a match and set the cauldron to burning. Let it burn for a few moments and then gather up some dirt or sand in your hands and toss it on the cauldron extinguishing the flame. Make sure the cauldron isn't hot to the touch and rub the sand all over it.
Don't forget to cackle and mumble to yourself a lot while doing this because you want to be sure to give that nosy old Mrs. Kravitz something to tell her husband about cause, you know, he lives for that shit. When you are done take the cauldron inside and wipe it out with a clean, dry cloth making sure all the dirt/sand is out of it. Pour a little vegetable oil in the cauldron and then rub the entire thing down with it and put the cauldron away to cure. Finally, when Mrs. Kravitz comes over to borrow a cup of sugar and casually ask what you were doing out there just smile and say "oh I've been inside with Tabitha all day, you must have seen my crazy cousin Serena!"