[Terrapreta] More on clay/pottery etc

[Michael Bailes]

Yes you are right. Logically,you would think if they went to the trouble of
grinding up charcoal they would do the same for pottery.
So what is the answer?
Shards would have to be fired to some extent surely?
Pottery made just for TP ? I don't know but would love to find out.
I doubt that firing temps would be much higher than that needed for
Terracotta. But I don't know.
There may be a bit on this In Amazonian Dark Earths if you can steal a copy

Here are a few posts I made on Hypography parent thread
I don't know if they get us anywhere.
mb

This is from a research article translated from Portuguese a bit hard to
follow
http://www.scielo.br/scielo.php?pid=...pt=sci_arttext<http://www.scielo.br/scielo.php?pid=S0044-59672004000200004&script=sci_arttext>

 Quote:
  most of mineral grains were taken from fresh crystalline rocks and
intentionally crushed and introduced into clay material as well as cauixi
and cariapé.

The above described minerals and organic substances led to identify the
following materials as raw materials for the ceramics:

1) clay material derived from weathering (saprolite/mottling zone) of fine
crystalline and less frequent sedimentary rocks (indicated by clay-derived
minerals and iron oxy-hydroxides, anatase and quartz );

2) fresh crystalline rocks crushed (feldspars, quartz and rock fragments);

3) organic materials (cauixi and burned cariapé).


The abundance of fresh feldspars, rocks fragments and roundless quartz
indicate that coarse igneous rocks, e.g. granites, granodiorites, and even
rhyolites and quartz of veins were used as temper, after crushing. It's
possible that pre-historic Indians extracted the fresh rocks from the same
place where they took the clayey saprolite.

To improve the plasticity of the raw material they introduce organic
material like cauixi and cariapé, crushed quartz, or even old ceramic
(waste) crushed, in an old process of recycling.
  .http://www.scielo.br/scielo.php?scri...72004000200004<http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0044-59672004000200004>
ABSTRACT

Several archaeological black earth (ABE) sites occur in the Amazon region.
They contain fragments of ceramic artifacts, which are very important for
the archaeological purpose.
In order to improve the archaeological study in the region we carried out a
detailed mineralogical and chemical study of the fragments of ceramic
artifacts found in the two ABE sites of Cachoeira-Porteira, in the Lower
Amazon Region.
Their ceramics comprise the following tempers: cauixi, cariapé, sand, sand
+feldspars, crushed ceramic and so on and are composed of quartz, clay
equivalent material (mainly burned kaolinite), feldspars, hematite,
goethite, maghemite, phosphates, anatase, and minerals of Mn and Ba. Cauixi
and cariapé, siliceous organic compounds, were found too.
The mineralogical composition and the morphology of their grains indicate a
saprolite (clayey material rich on quartz) derived from fine-grained felsic
igneous rocks or sedimentary rocks as source material for ceramic artifacts,
where silica-rich components such cauixi, cariapé and/or sand (feldspar and
rock fragments) were intentionally added to them.
The high content of (Al,Fe)-phosphates, amorphous to low crystalline, must
be product of the contact between the clayey matrix of pottery wall and the
hot aqueous solution formed during the daily cooking of animal foods (main
source of phosphor).
The phosphate crystallization took place during the discharge of the
potteries put together with waste of organic material from animal and
vegetal origin, and leaving to the formation of the ABE-soil profile.

I was wandering arround the Permaculture forums and came accross this post
which is interesting.
You should vist the site if you are into useful plants and gardening. It's
great
SEE:
http://forums.permaculture.org.au/vi...?p=18201#18201<http://forums.permaculture.org.au/viewtopic.php?p=18201#18201>

Re: Terra Preta What is the fuction of the clay pottery shards?

"PostPosted: Wed May 03, 2006 11:26 pm
On reading about the actual terra preta mix and process there are a lot of
questions about the presence of clay shards. I havent even read any
speculation as to why they are there.
Two, things spring to mind.

Firstly, the ancients may have been carting this soil to other areas or
water to that site but woven baskets would have been more feasible for the
soil.

Secondly and more likely, possibly part of the reason for the burning was
that this was the place that clay was fired. Once a pot was broken they
could have been smashed over time or used as 'heat beads' in the next
firing. The refined pottery we use is fired at incredible temperatures, this
may not have been known to these people and their climate was not condusive
to sun drying [which can take months].

Just idle speculation I doubt the ancients would have deliberately tried
build soils but they may have been building pots and stumbled across a
symbiosis in their process which lead to the terra preta.

I would love more speculation or clarification if anyone has tracked down
why the clay shards appear through this mix. The show I saw on terra preta
didnt mention them, only found it in further reading.

Cheers

Floot
mb

On 10/05/07, Allan Balliett <aballiett at frontiernet.net> wrote:
>
> >I think clays are acid while charcoal tends to be alkaline so there
> >may be a clue thery to why it was used in TP. Like charcoal it also
> >has adsorption properties.
> >If anyone could point me to reach aricles wher it was used as asoil
> >amendment i would apreciate it
>
> Michael - I've received contradictory information on whether or not
> the shards in Terra preta had been fired or not. I understood Charles
> C. Mann to say that they were not fired and the many of the shards
> were not from pottery but apparently made in sheets  for terra preta
> use (only). From other sources, including general archeologists I
> hear that 'all pottery is, by definition fired"
>
> My 'point' here is sort of: if the makers of terra preta wanted to
> incorporate clay for clays sake and they were already pulverizing
> char to 1x1mm, wouldn't they as well pulverize clay (or add in in a
> natural state) rather than include it in large pieces? Large pieces,
> which, the vary 'largeness' of could have a function outside of
> chemistry or nutrition?
>
> -Allan
>



-- 
Michael Bailes.
"Human beings,
who are almost unique in having the ability to learn from the experience of
others,
are also remarkable for their apparent disinclination to do so."
Douglas Adams, "Last Chance to See"
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