Has anybody melted old crayon remains and poured the wax into water-saturated plaster molds to make new large mural crayons?
This is may not be safe for students unless they are carefully supervised older students, but teachers can do it if you follow safe wax melting practice. Melted wax can easily get too hot and never should be heated directly on a stove top or hot plate. It can splash, can burn flesh off the hands and face, etc. Limit wax temperatures to no more than 200F. Some use an old slow cooker. Some use a double boiler set up.