[Terrapreta] torrefaction vs. carbonization

[Greg and April]

That makes two of us that are not experts.    < grin >

I was just thinking of the similarity between them - long hours at low temperature, followed by a rapid rise to a high temperature, then a fairly rapid cooling.

Greg H.

  ----- Original Message ----- 
  From: Gerald Van Koeverden 
  To: Greg and April 
  Cc: Terrapreta preta 
  Sent: Saturday, December 08, 2007 19:42
  Subject: Re: [Terrapreta] torrefaction vs. carbonization


  Greg,


  Am not an expert, but from a very cursory check, it sounds more like that there are three types - grey, black and white - each one progressively harder than the one before, as higher temperatures are used in the carbonization process.  Any experts out there??


  "Today, Japan's charcoal-making techniques are admired worldwide. We can classify the different types of charcoal used in Japan into two broad categories: kuro-zumi (black charcoal) and shiro-zumi ("white" charcoal).
  Generally, black charcoal is soft and retains the tree bark. It is easy to ignite, and burns hot enough for metal smelting and blacksmithing. Almost all of the charcoal produced around the world is similar to this type. To make it, the wood is carbonized at temperatures between 400 and 700ºC, then the kiln is sealed until the burning stops and the heat slowly dies away. One type of black charcoal used in the tea ceremony, ikeda-zumi, is favored for its beautiful appearance. It is made from a kind of oak in the northern part of Osaka Prefecture.
  White charcoal 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. This explains the name "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."


  from:  http://web-japan.org/nipponia/nipponia19/en/topic/index.html


  Gerrit


  On 8-Dec-07, at 9:11 PM, Greg and April wrote:


    It sounds simular to the process of making 'white charcoal' that I read about a couple of day's ago.

    Greg H.
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