Slice a bottle in half ... with string | Wonder How To
http://www.wonderhowto.com/wonder-of-the-day/cut-a-beer-bottle-in-half-with-a-string
"The ingredients necessary are simple: string, acetone and a match. ... The clean break in the glass occurs when the exact ring of heated glass comes in contact with the cold water. Thermal shock slices the bottle in half."