How it Works
How charcoal filters water:
Wood and plants like bamboo, have a large number of vessels that carry nutrients up from the earth when the plant is alive. During the charcoal-making process, the wood is heated without oxygen, and as it slowly carbonises, it leaves these fine vessels intact in a highly permeable structure. It is considered that 1g of charcoal has a surface area equivalent to 3 tennis courts. As water roams through the myriad porous cavities, impurities such as chlorine are trapped in the cavities, removing the familiar chemical taste of tap water.
Unlike many filters, the water is not poured through the charcoal, but the charcoal remains in the water for several hours, so giving it time to filter the water fully. The difference in temperature between different parts of the jug will cause a convection current which keeps the water circulating, even though its movement may not be noticeable to the eye.
How water-filtering charcoal is made :
All charcoal has water filtering properties in theory but most types are too dusty and crumbly to be practical for drinking water filtration. Most barbeque charcoal which you can buy in DIY shops and garages has been mass-produced (quickly) and often the porous cavities are not very fine or have been destroyed in the process. Of course, this is not a problem if you are using the charcoal simply as fuel, but it would not be suitable for water filtering.
Charcoal that is suitable for drinking water filtration is usually made by experts with years of experience using traditional methods and clay kilns. The whole process takes up to 2 weeks during which the temperature is raised gradually and towards the end of the process reaches as high as 1000 degrees. This exquisitely careful process turns wood and bamboo into high quality charcoal with its fine porous structure intact. Charcoal made in this way tends to have a silvery sheen and is harder and heavier than ordinary charcoal, and once washed it is dust free.
Why bamboo?
Other woods, including types of Japanese oak can be used to make charcoal for filtering water but bamboo charcoal is considered to have better filtering abilities than other types because it has a larger number of porous cavities. In fact, well made bamboo charcoal has a surface area three times greater per gramme than good quality wood charcoal. Bamboo is also a very fast growing plant and not endangered, and so supply is abundant and sustainable.
