In a very small-scale experiment I did on ancient baking and fire quenching
in Egypt, I discovered that controlled quenching of a small contained fire
with water was unsuccessful: lots of smoke and steam were produced but the
coals continued to glow and heat was still produced for some time. Also,
the work area was a big mess after that. Then I tried quenching by throwing
sand over the coals - this was much more successful and instantly quenched
the coals (lack of oxygen). This method seems to get some support from
archaeological evidence in an ancient Egyptian bakery excavated at the time
I tried out this experiment: in some areas the excavators found lenses of
charred material interspersed with lenses of sand.

Of course, different ancient methods might have pertained in different
climates and working set-ups. But the rapidity of fire quenching, whether
by cooling or some other method such as smothering, might also have an
effect on charcoal structure.

Delwen


At 19:27 09/09/2004 +1000, you wrote:
>Archaeobotanists
>
>When I use the term wet wood to refer to dry wood that has been
>wet(rain, dampness ...), in other words wood that is dead when
>collected, but has high moisture content from external conditions. Green
>wood refers to wood that has been collected while living tissue is still
>present and whose moisure content is from the normal physiological
>processes internal to a woody plant.
>
>Whether the water source makes a functional difference to combustion and
>carbonization is uncertain. Water is water, but some of the volatiles,
>etc., present in green wood surely are not be present in wet wood. Some
>woods have a reputation to burning when green, others to burning when
>wet, but off the top of my head I can't remember any that have a
>reputation for burning when green or wet.
>
>Dr Dufraisse raises a fascinating point, is fusing (glassiness) a result
>of immediate post-carbonisation processes, as well as or instead of
>taxa, chemistry etc. In my burning experiments I have never attempted to
>suddenly cool the charcoal, always allowing a gradual cooling, and there
>is certainly more fused charcoal in archaeological material than
>experimental material I have looked at.
>
>There is an enormous amount of science of carbonization not just of
>cellulose but of other wood components and of whole wood, though far
>less of large "firewood" sized material. Perhaps I should publish a
>bibliography.
>
>Can any anglophones out there publish a summary of Théry -Parisot's work
>for us regrettably poor-francophones.
>
>nic
>
>"Dr. Alexa Dufraisse" wrote:
> >
> > Hello everybody,
> > I am a new member of the archaeobotany list. My name is Alexa
> Dufraisse, I am
> > french (so excuse for my english) and my work is focussed on charcoal
> analysis
> > in waterlogged sites, especially located in the circum-alpine area in
> Europe.
> > At the moment, I am working in Basel (postdoc) at the lakes of Zürich and
> > Constance.
> >
> > I just have read your discussions about the glassy charcoal. There is
> another
> > hypothesis about the vitrification of charcoal : a quick cold growing for
> > example by water. Is there someone which had worked on this problem? I have
> > also worked on salt spring exploitation in the french Jura. I did with the
> > collaboration of archaeologists few experimentations. They showed that
> in order
> > to crystallize salt, we have to water the hearth with salt water which
> creates
> > a cold. But, among the experimental and archaeological charcoals, I did not
> > observed more glassy charcoal....
> >
> > I have another question : what is in English the difference between wet
> wood and
> > green wood? Is it a problem of the percentage of the humidity or
> between living
> > trees and "just cut trees" or other....?
> >
> > Best regards
> > Alexa Dufraisse
> > --
> > Alexa Dufraisse
> > Universität Basel
> > IPNA, Institut für Prähistorische und Naturwissenschaftliche Archäologie
> > Spalenring 145
> > CH-4055 Basel
> > Tel +41 61 201 02 17
> >
> > ----------------------------------------------------------------
> > This message was sent using IMP, the Internet Messaging Program.
>
>--
>Nic Dolby
>
>School of Geography & Environmental Science
>Monash University
>CLAYTON, VIC., 3800
>Tel.: +61-3-9905-2919 (or Dept Office +61-3-9905-2910)
>Fax: +61-3-9905-2948
>Email: [log in to unmask]

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Dr. Delwen Samuel
Institute of Archaeology Division of Life Sciences
University College London Franklin-Wilkins Building
31-34 Gordon Square King's College London
London 150 Stamford St.
WC1H 0PY London
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