Black charcoal, white charcoal... Classified by surface colour

Depending on such factors as the method of preparation and materials it is made from, charcoal is roughly classified into three types under the Japanese Agricultural standards(JAS).
The newest type of charcoal is the artificial oga charcoal, made from wood chips and employing thermal compression and carbonization. Historically, though, one of the original charcoals was "black charcoal", carbonized from such broadleaf timbers as kunugi oak, Japanese chestnut, and kashi oak. This is a porous charcoal, which took its name from its deep black hue. Black charcoal is characteristically easy to ignite but has poor heat retention. The third type of charcoal is "white charcoal", typified by binchotan. Based on such broadleaf woods as Japanese holm oak, nara oak, and kunugi oak, this is made only inside a special earthen kiln then extinguished on sand outside the kiln. The charcoal that results is known as "white charcoal", so called because of its light-coloured ash coating. This charcoal has a silver-grey interior, is hard, and when tapped, gives off a metallic sound. While difficult to ignite, white charcoal maintains high temperatures during combustion and has extremely good heat retention.