lol i stick my lighter or finger in the bowl, i always had trouble telling if a bowl was cashed or not and i think in my early years of smoking i probably threw out some still-burning bud because i just didn't know. It's cashed if when you stick your finger in the bowl you dont feel anything hard in it at all, its just all grey-white ash. if you think it might be, take a pen or something and stir the bowl and see if it helps