Binchotan is made by charring the wood at a relatively low temperature for some time, then, near the end of the process, raising the kiln temperature to about 1000ºC to make the wood red-hot. The charcoal is then pulled out and quickly smothered with a covering of powder to cool it.
The powder is a moist mixture of earth, sand and ash, and gives a whitish hue to the charcoal surface. That is why binchotan is also known as “white charcoal.” The rapid rise in temperature, followed by a rapid cooling, incinerates the bark and leaves a smooth, hard surface. If you strike it, you’ll hear a clear, metallic sound.