They grabbed ink bottles and sprayed the class with them, shredded books and papers, tore pictures from the walls, up-ended the waste bin, grabbed bags and books and threw them out of the smashed window.
Eventually, it gets so hot that the atoms in the steam, the air, and even the grape juice have their electrons stripped off, and you get a bunch of plasma.
Quickly, wondering if this plan could possibly work, Harry took off one of his shoes, pulled off his slimy, filthy sock, and stuffed the diary into it.