[Terrapreta] Potsherds

[Ron Larson]

Kurt etal

    A nice job of exploring the various explanations.  Thanks.  I enter the 
conversation  as the husband of a full time potter - with some experience in 
low temperature firing myself.

    In addition to your list, I'd like to know if there have been any 
forensic investigations on the pottery.  I wonder what portion show evidence 
of use. (the rest breaking during firing.  (my wife guesses that most made 
it through the firing).    I'll bet that local investigations could identify 
the sources of the clay.  My wife's clay has about ten ingredients - it 
wouldn't surprise me that these pots had one.  But these could be quite 
different clays near different villages.  It shouldn't be too hard to get 
local potters to replicate pretty closely the pottery seen there - which 
probably could tell a lot about the means of firing,  including temperature, 
and time.

   My own guess is that the biochar is a lot more important for productivity 
than the pottery - which even if extensive is probably not uniformly 
distributed.  I say this mostly based on guesses on porosity (internal 
surface area) and what I have heard about the importance of charcoal itself. 
I have read the two big thick "Black Soil" books, which contain some 
anthropological discussions, but don't remember any papers getting into this 
level of detail.

        I hope someone can tell us they have tested soil productivity with 
and without different amounts of ceramics.   Until I hear some differences 
in those tests, I am going to put more emphasis on the char - which I am 
guessing may out-weigh the ceramics by 100 to 1 and provide cavities by an 
even larger margin.  I see the main value of the ceramics as being proof 
that there was human involvement in the soil production.

    What intrigues me most is whether we can find proof that the char is 
present because of conscious intention.  Some can't see this as an 
invention - but rather that Terra Preta just "happened".  I lean the other 
way.  Pottery investigations might help answer that important question.

Ron


----- Original Message ----- 
From: <rukurt at westnet.com.au>
To: <terrapreta at bioenergylists.org>
Sent: Thursday, March 29, 2007 6:57 PM
Subject: [Terrapreta] Potsherds


> Hi folkes,
>
> One of the things that are found in Terra Preta  Dos Indios is pottery
> sherds. We believe that because of their porosity they also assist with
> the job that charcoal does, and without a doubt, it does.
>
> How did they get there?
> Were they deliberately added, or were they a handy form of garbage that
> was chucked in with the charcoal.
> Was the charcoal a byproduct of pottery firing?
> Were the potsherds deliberately produced in the manufacture of the
> charcoal, in charcoal kilns?
>
> Apparently the type of pottery is quite low quality, produced by low
> heat firing. How does this compare with normal pottery of the times?
>
> In New Guinea, the people of Aibom, a village on the Chambri Lakes, off
> the Sepik River make pottery which, when dry is  laid out, covered with
> lots of dry coconut palm fronds and these are burnt. The resultant
> pottery is very soft and fragile, but very popular with the tourist. A
> lot of it breaks in the firing and if the Indio pottery was similar,
> there would be a lot of broken pottery to further smash up and chuck in
> the ground.
>
> On the other hand, if they used pottery kilns, of built from cob clay
> for instance, there would be better pottery, but there would still be a
> lot of breakages. Bronze age Britons did it this way in Aulde (very
> Aulde) England.
>
> Charcoal may have also been made in kilns and pottery could easily have
> been placed in them to be fired (dual use kilns?) again producing the
> inevitable broken pottery.
>
> How can we add pottery to our terrapreta charcoal?
> Broken pots are an obvious source, but plastic pots don't qualify.
> What about broken bricks? Perhaps even from the demolition of old
> houses? Beware of Lead contamination from roadside walls though, and
> perhaps Copper contamination from electric tramway sites.
> Painted bricks could also be lead contaminated.
> If you use a TLUD charcoal burner, you could add a sprinkling of dry
> clay bits to the fuel and it would get fired along with the charcoal
> production. Some people recommend putting ceramic balls on top of the
> fuel load to control the burning. They could be unfired clay, if you
> find that beneficial.
> Other forms of charcoal makers (retorts) could also have bits of unfired
> clay added.
> Then again, all methods of charcoal production produce excess heat and
> also often burnable gases, which could fire a proper pottery kiln.
>
>
> Think about it
>
> Kurt
>
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