I soften the edges of the 20 oz water bottles and 2 liter bottles that I've cut in half by carefully and slowly running my lighter over the edge. I'm careful not to inhale any smoke. I quickly blow out any small flames. I thoroughly cool the bottle before touching it. Once you've softened the edge it is completely touchable and easy on your fingers.
I soften the edges of the 20 oz water bottles and 2 liter bottles that I've cut in half by carefully and slowly running my lighter over the edge. I'm careful not to inhale any smoke. I quickly blow out any small flames. I thoroughly cool the bottle before touching it. Once you've softened the edge it is completely touchable and easy on your fingers.