[Terrapreta] torrefaction vs. carbonization

[Gerald Van Koeverden]

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.
> _______________________________________________
> Terrapreta mailing list
> Terrapreta at bioenergylists.org
> http://bioenergylists.org/mailman/listinfo/ 
> terrapreta_bioenergylists.org
> http://terrapreta.bioenergylists.org
> http://info.bioenergylists.org

-------------- next part --------------
An HTML attachment was scrubbed...
URL: /pipermail/terrapreta_bioenergylists.org/attachments/20071208/6a889243/attachment-0001.html