Gravity bong

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In cannabis culture, gravity bong is a term that can refer to either of two devices used for smoking cannabis that use the gravitational force of water to create a vacuum whereby the suction created draws air through a bowl to fill the container with smoke.

Gravity bongs differ from regular bongs in the fact that they usually do not filter the smoke through water, they have a far larger chamber, the smoke is much denser than possible in a standard bong, and they are usually homemade. Additionally, rather than the operator reducing the air pressure inside the device through inhalation, this is achieved with either falling water or by lifting the device itself while it is partially submerged in a bath of water.

[edit] Terminology

Gravity bongs are named for gravity's role in their function. Upon using a gravity bong, suction is created when trying to restore the pressure equilibrium of the inside of the bottle with the outside air. Both devices described below are known as gravity bongs and not all people will be familiar with both versions; many may know their device as a gravity bong instead of using the more specific term for each device. While both methods share similarities that are critical to their operation, they differ in the technique that is used to control or constrain the rate of air flow through the bowl. Gravity bongs originated in Gloucester Virgina AKA G-town.

[edit] Bucket method

A Variety of the Bucket Method; Bucket Gravity Bong with percolating tube, ping-pong water guard and bubbling hitter piece. "

A gravity bong utilizing a bucket can be constructed in many different ways, allowing for variations in material availability.

It is a little known fact that a standard gravity bong can be modified so that the water is used to do more than simply create a vacuum. In the "Blissett Bucket" a downtube is inserted and the water is used as a filter too. To see a guide to building one of these, please click here (it is believed that this was invented in 1996. A forum thread about it exists here)

In all cases, however, some sort of a bottle and a bucket are needed. The size of the bottle is very important to operation; a larger bottle is generally preferred. The larger the bottle is, the more volume that is available to fill with smoke. The size of the bucket is contingent on the bottle; it is ideal that the bucket can, when filled with water, allow the entire bottle to be submerged.

The bottle is prepared by cutting the bottom of the bottle off, leaving it as tall as possible. Also some sort of bowl or stem is somehow placed in the bottle cap, usually by cutting a hole. It is absolutely vital to the proper operation of the gravity bong that the seal on the hole in the cap is air tight, such that the only air that can enter through the cap is through the bowl or stem. Also common is a small hole placed near the top of the bottle to be used as a shotgun or carb. The purpose of this carb is to allow clean air into the bottle from another source other than the cap, and to keep water from entering the mouth of the user if they inhale too forcefully. A simpler method is to remove the cap and place tin foil over the bottle top. The foil is shaped into a bowl shape, pierced with small holes, then filled with cannabis. Another method for making the bowl for a gravity bong is to use a two liter bottle, and use a knife to cut a large hole in the cap of the bottle. You can then use a salt or pepper shaker top for the actual bowl, giving you a lasting and safe bowl that works every time. Half of a capsule tea strainer is also particularly effective, especially since its mesh or holes are designed to be just small enough that shredded tea leaves (which are often the same size as shredded marijuana leaves) don't slip through. The one drawback to both bowls is that, owing to their considerable size (compared to glass stem bowls), matches or grill lighters are required to light them. When placing the cap onto the bottle, it is not necessary for the bowl to be screwed onto the lip of the bottle fully. If a sufficient and even hole has been made, there will be no need for sealers of any kind.

The bong is operated by submerging the bottle in the bucket, with only the open top of the bottle protruding from the surface of the water. The bowl is filled with a substance to be smoked and then screwed onto the top with the bottle still in the water. The bottle is then slowly lifted out of the water while the carb is being covered with a finger, at the same time as a flame is applied to the bowl. Some people prefer using a butane or "torch" lighter to further enhance combustion of the material, making the "hit" even more dense. The speed at which one pulls the bottle up depends on how dense of a hit is wanted, and how well the material is burning. Generally the rule of thumb is to pull fast enough that the material is burning and smoke is flowing into the chamber, but slow enough that the "hit" will be dense. The pressure will pull the flame into the bowl, burning the substance and pulling all of the smoke into the bottle. Once all of the material in the bowl has been burned or the bottle is full of smoke, the cap is removed, the user exhales all air out of the lungs, and then places his or her mouth over the opening. The bottle is then pushed down into the bucket, forcing the smoke into the user's lungs.

A pictorial diagram of how gravity bongs operate.

When the bottle is pulled out of the water with the carb covered, the air flow into the bottle is restricted to whatever is allowed through the bowl. Any air that enters the bottle must come through the burning material; thus the air is consumed during the combustion process and the only gas that enters the bottle is very dense smoke. Typically the amount of smoke entering the bottle is not enough to account for the change in volume which results from pulling the bottle out of the water. Thus to keep the pressure inside the bottle the same as the surrounding air the water level inside the bottle raises above the water level of the rest of the bucket.

The force of gravity's pull on the water inside of the bucket creates the suction that pulls air through the bowl. The force of the suction is directly proportional to the level that the water in the bucket is raised above the surrounding water level. The higher the water level is pulled creates a higher force due to gravity, because of a larger volume of water being suspended higher.

The pressure inside the bottle is governed by the equation , where p is the pressure of a fluid column, ρ (rho) is the density of the fluid, g is the gravitational acceleration, and h is the height of the fluid column. As the water levels in the bottle and bucket separate, the difference in height causes a pressure difference between the bottle and the atmosphere. A larger pressure difference means that air will be sucked through the bowl at a higher flow rate which is not always ideal. A high rate of air flow may result in the substance in the bowl burning faster than is ideal to maximize the amount of smoke. Another complication resultant from excessive air flow may be the substance is pulled through the opening of the bowl before it is fully burned, producing wasted material.

After the bottle is full of smoke, and all combustible material is burned, the user forces the smoke into their lungs by pushing the bottle down. The effect that is produced from pushing the bottle down is the opposite obtained from pulling it. When the bottle is pushed down the water level in the bottle is pushed lower than the top of the water, which results in the gravitational forces on the surrounding water to force the water level back to equilibrium in the bottle. To maintain equilibrium, the gas in the bottle is forced out the now open top into the lungs of the user at a higher force than usual. Alternately, some users prefer to suck on the mouth of the bottle, drawing both smoke and water upwards. If the bottle is equipped with a carb, the water level will only rise to the level of the opening. Otherwise, great care must be taken if the user does not wish to draw water into the mouth.

Bucket gravity bong with simple homemade soda-cap & socket hitter piece; and Northern Lights cannabis.

According to some, this bong maximizes the effect of the substance smoked like no other method can. This is due mainly to a number of factors, the enormous density and volume of the smoke, and the velocity at which the smoke is forced into the user's lungs. Therefore, gravity bongs are generally known for producing a very intense experience - one which a regular bong cannot. A gravity bong produces a hit that contains much more volume than one produced from normal methods, because the user usually stops before they've sucked in a gallon of smoke, however a gravity bong is a large bottle, completely filled, thus ensuring a maximum potential for a "huge hit". Critical to the large volume is the high density of the smoke which is produced due to the restricted source of air flow, only through the bowl. Combining these factors with gravity forcing the smoke into the user's lungs at an increased rate, the outcome is a method that surpasses any other in the amount of effect that produced from the smoked substance.

[edit] Accessories and modifications

Optional bucket bong accessories include a bong water guard. A guard consists of a buoyant sphere, often a ping-pong ball, that is placed within the bottle before the hit is drawn. Slight modification of the bottle will keep the ball inside the bottle at all times. Instead of having the entire bottom of the bottle cut off, wedges of the bottom may be cut out. When flat, they will not allow the ball out, but when gently twisted the gap is large enough to allow pong ball access in and out of the bottle.

Another modification is a percolation tube that draws the smoke down into the water by connecting to the male slide piece. This is often called a "Blissett Bucket, after Luther Blissett, an internet alias used by someone who is thought to have invented the device in 1996. "The bottle must be raised so that the mass of the volume of water inside the device above the water's surface can gravitationally pull the smoke through the percolation tube. If the tube is long or the device is not airtight, it will not work. This method produces a toke that is generally more potent and also decreases the damaging heating effect of the conventional gravity bong."^{[citation needed]}

[edit] Other vacuum methods

As with the waterfall method, the bucket method uses gravity to create a vacuum. Its claim for the title of "gravity bong" is supported mainly by the argument that it relies more on the force of gravity. The bucket method uses gravity's pull both to create a vacuum, and to control the air flow. When the bong is pulled using the bucket method, the air flow rate is directly proportional to gravity's force due to the difference between the water levels of the bottle and the surrounding bucket. Some argue that the bucket method in fact does not need gravity at all. All it needs is a device to create a vacuum; therefore it can also be referred to as an air displacement bong, or pressure flux bong. Gravity merely holds the water in place (making it resemble a liquid piston). If a solid piston is used instead of the "liquid" piston, the direction of gravity is irrelevant. Attaching a plastic bag to the end of interior plastic bottle of the bucket bong would serve as this solid piston, a bong commonly referred to as the lung.

[edit] SoBe Bottle

A common and cheap use of gravity bongs is to use a modified SoBe bottle. The user creates a small hole on the bottom of the bottle, where a small "bump" is. They will alter the top cap of the bottle with a tobacco filter and small funnel to hold the the cannabis.^[1]

The bottom hole is sealed, generally with a finger, and the bottle is filled with water. Then they will "pack the bowl" in the top funnel. After, they will use a lighter and light the cannabis, once they let go of the hole the water will drain and the bottle will fill up with smoke. Once the bottle is drained they will take off the top and inhale the smoke.

[edit] Health Issues

Because gravity bongs usually use plastics and possibly aluminum foil or cans, PVC pipe, plastic tubes or garden hoses, and many other household products not intended to be heated, it is likely that the user will inhale fumes more dangerous to their health than the intended cannabis.

[edit] Notes

1. ^ http://www.geocities.com/legalizetheplant420/gravity.html

[edit] References and further reading