Magic Erasers are actually made of melamine foam, which has been used for decades as an insulation and soundproofing material. About 10 years ago, some smarty-pants discovered that melamine foam was also an effective abrasive cleaner! It works because when melamine resin cures into foam, its microstructure becomes almost as hard as glass — causing it to act like a SUPER-fine sandpaper on stains. The abrasive foam loosens up dirt and grime, and the open microstructure of the foam sucks it in and traps it there.