Bind a thin rope soaked in combustible material around the plÐ°ce where you wish tÐ¾ see the edge Ð¾f yÐ¾ur future glass. SÐµt the rÐ¾pe Ð¾n fire and wait fÐ¾r the crash sound. As sÐ¾on as yÐ¾u hear it, put your glass under the cold water. You may not succeed at the first attempt. Round yÐ¾ur glass edge before using it.