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A water pipe or bong is a device used for smoking, usually cannabis (and less frequently tobacco), in which smoke is bubbled through a chamber containing water.
Principles of operation The user inhales with their mouth sealed other an opening. This reduces the air pressure in the chamber of the bong above the water level. To equalize the pressure, the atmosphere pushes the heated air (from a flame) through the combustible matter, forming smoke. The smoke then bubbles through the water, into the chamber. For example, if one 'bubbles' a glass of milk with a drinking straw ('bubbling' is placing the straw beneath the surface of the milk and blowing), they are demonstrating the same physics but they are assuming the role of the atmosphere and not the bong user.
Motivations for operation Bubbling the smoke through water serves to cool down the smoke, which is typically very hot, and to trap some of the heavier and more water-soluble particulate matter, keeping it from entering the smoker's lungs. One may also pack the bong with ice, and then add water, to cool the smoke even more. For this reason, some users claim that cannabis smoke filtered through water is safer than unfiltered cannabis smoke. There is little evidence for this claim however, and there is anecdotal evidence supporting that bongs put larger forces on the lungs than do rolled cigarettes, and so therefore are more damaging. Doctors tend to prescribe cannabis cigarettes, for example, over other delivery methods (including ingestion).
Bongs have been constructed out of many different materials, often improvised from simple household items like soda cans and garden hoses. However, concern has arisen recently that PVC plastic piping, which is often used in bongs, may release poisonous dioxins when it exposed to hot smoke.
While scientific research is scant, alternative materials that could be used instead of plastic are: glass, ceramics, stainless steel, or even bamboo, as all are much less likely to add to the harmful content of smoke. All metals can ionize or vaporize in sufficient heat, potentially transfering metal to the user's lungs. To date, metal-containing bongs have not been widely implicated as a source of heavy metal toxicity (the proposed link between aluminum and dementias is poorly founded, as proteinmyoglobin, showing coloured alpha helices. This protein was the first to have its structure solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, which led to them receiving a Nobel Prize in Chemistry. A protein is a complex, aggregates seem to trap a wide rangth of metal ions, and aluminum is the most abundant metal in the Earth's crust).
Water pipes derive their heritage from the classical Arabic hookahCaterpillar using a hookah An illustration to Alice's Adventures in Wonderland by Lewis Carroll A hookah or narghile ( Persian nrgile < nrgil "coconut", itself borrowed from Sanksrit nrikera is an Middle Eastern water pipe. It is also known as a shisha (, which was originally designed for smoking tobacco and other flavored smoke producing materials. Bongs differ from hookahs in that they are usually simpler, with a single mouthpiece on the water chamber rather than a hookah's one or more hoses.
A gravity bong is a different smoking device which also uses water. They are almost all home-made and are rarely available commercially. A gravity bong is made of two different containers, most typically a bucket and two-liter soft drink bottle (when constructed with a bucket they may be referred to as a bucket bong). The bottom of the bottle is cut off, and the cap is made into a device capable of holding the substance to be smoked. The bucket is filled with water, and the bottle placed in the water so the missing side is underwater and the cap, filled with the substance to be smoked, is above it. The substance is lit by one person while another slowly and steadily raises the bottle, careful not to bring the edge of the open bottom above the water level. The increasing volume of waterless-space inside the bottle pulls smoke from the cap into the bottle. The cap is taken off, and one person inhales the smoke inside the bottle, often while plunging the bottle back into the bucket (in order to force more smoke into the lungs).