When smoking through a bowl, how do you know when the marijuana (THC)has been used up and ur not just lighting and smoking ash?
You can tell from the taste, if nothing else. I just turn the bowl upside down and tap it with my lighter. The ashes will fall out but the weed will usually stay in there, if it is packed correctly. Also, ashes don't cherry, weed does. So if there is a cherry in there then you still have some weed to smoke.
its easiest to just continue trying to light the weed until it doesnt light anymore, then your done... maybe stick your pinky in the bowl and stir it around a bit, try to light it again... if nothing again then your defiently done