Cleaning Potions

Cleaning potions are potions which, as implied by their name, clean various surfaces. Many include diluted Bundimun secretion, a highly acidic substance that comes from Bundimuns, small magical parasites. One particularly prominent cleaning potion is Mrs. Skower's All-Purpose Magical Mess Remover, which goes by the slogan "No Pain, No Stain". It is presumably effective, as a stock is kept at Hogwarts, but in some instances, it does not work. When Ginny Weasley writes on the wall in blood under Tom Riddle's influence, the words will not come down, no matter how hard Argus Filch scrubs with Mrs. Skower's Magical Mess Remover. It is likely that other cleaning potions are the same; good for stains, but not infallible.