[Terrapreta] More on clay/pottery etc

[Kevin Chisholm]

Dear Michael

Heres an "outside the box" thought...

Is it possible that people had large charcoaling operations, where they 
retorted the biomass in pottery retorts, and simply discarded the fines 
and broken retorts into a dumping area?

Then later on, someone noticed things growing on the areas where 
charcoal fines had been dumped, after the Charcoal operations were 
abandoned.  They would then graze their animals on the grass, and the 
manure would provide nutrients to support the process.

Why would the Terra Preta beds be 4' to 6' thick? Farmers are smart and 
observant. In the Olden Days, with no mechanization, they would find 
ways which gave acceptable growing results, with the least inputs. It 
takes a lot of work to build a Terra Preta bed 4' to 6' thick, just to 
grow crops. It does not make sense that they would build the Terra Preta 
beds any thicker than necessary. I would suggest that it is simpler to 
dump waste charcoal fines and broken pottery in a low lying spot in the 
land, than to spread it uniformly, than retain the uneven ground surface.

The above seems to be a more credible explanation for the formation of 
Terra Preta fields. It explains why Terra Preta beds could be 4' to 6' 
thick, when such thickness are not necessary for growing crops.

So, I would pose the following hypothesis for your consideration:

1: In the past, charcoaling operations made charcoal in pottery retorts.

2: The market was for larger pieces of charcoal, so they screened out 
the fine charcoal and discarded it, simply by dumping on the ground.

3: Similarily, when the pottery retorts were damaged or broken, they 
would discard them in the same areas where they dumped charcoal.

4: They would favor low depressions near the retorts, in that they would 
hold a lot of charcoal fines, and the workers wouldn't have to walk as far.

5: The means of transport of charcoal fines would probably be by baskets 
carried on the heads of the labor force. It is relatively easy to carry 
such a load over level ground. It would be easier to walk a bit further 
on the level rather than walking uphill.

6: The presence of terra cotta or pottery shards is incidental to Terra 
Preta, and not essential or even necessary.

7: Charcoal retorts were made from clay, and were fired to pottery with 
the off-gasses from the retorting operation. Sometimes, when a retort 
was fired too quickly, it would break, and the partially fired retorts 
would be discarded.

Can anyone find errors in the above hypothesis? Can anyone add to it?

Best wishes,

Kevin

Michael Bailes wrote:
> 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
>>
> 
> 
> 
> 
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