With a gravity bong one uses water pressure to create the vacuum in a chamber rather than the lungs.
Gravity Bong 1>> A gravity bong is made with a 2 litre bottle with the bottom cut of. You need to heat up the plastic top and then push a cone piece into the screw top lid, this needs to a be a perfect seal so push it in when the lid is really hot. The open bottom end is placed in a bucket of water and pushed down so that the top is only a couple of centimetres from the water level. Fill the cone piece with a bud. Then put the lighter to the bud and pull the bottle upwards until the large opening of the bottle is about 3cm away from the surface of the water. This will draw smoke into the chamber like a vacuum. Then to inhale the smoke simply unscrew the top put your mouth over the small opening and push the bottle down so that your mouth is close to the water level. The smoke is actually pushed deep into your lungs, you may not blow out any smoke at all. You will feel very stoned.
Gravity Bong 2>> Get another 2 litre "rocket based" bottle and burn 4 holes into it all about the same size as a large thumb nail. You need to then heat up the plastic top and then push a cone piece into the screw top lid, this needs to a be a perfect seal so push it in when the lid is really hot. Fill the entire bottle with water, easiest to push it into a bucket/sink full of water. Pack a bud into the cone, then let the water drain out through the holes in the bottom this will suck smoke in through the cone piece at the top. When there is about 3 inches of water left in the bottle put it back in the sink/bucket, keep it at 3 inches of water, take the screw top off with the cone piece and then inhale the smoke from the bottle top while the remaining water drains and bubbles its way out. For some reason you get a really clean hit, totally smooth.
Note: This is not a healthy way to use marijuana. Pushing the smoke and tar so far into your lungs is even worse for you than normal tokes. Try the vaporizer instead.
