search  current discussion  categories  kilns & firing - misc 

need test of how pot was fired (formerly: need new source of fuel to

updated sat 9 nov 02


Spencer H. MacCallum on thu 7 nov 02

replace manure)

Shelley Corwin writes that the potters of Mata Ortiz are running out of cow
chips and are prohibited by law from using dead cottonwood bark. But there
are many alternatives. The scarcity argument is largely a rationalization on
the part of those who are tempted to use commercial kilns. Juan Quezada
insists, just as Stephani Stephenson suggests, that there's an abundance of
dried vegetal material of all kinds. He's developing a simple method of
making grass cakes ("synthetic cow chips") utilizing the grass and weeds
that are regularly mowed on the sides of the highways to discourage cattle
from grazing close to the traffic. With a bit of maguey juice binder (years
ago when he first tried this he used a little clay water), he compresses
this into cakes which, when sun dried, he says have better burning quality
than cow chips.

By numerous pyrometer tests, incidentally, we've found the temperature in
the Mata Ortiz method of firing in cow chips peaks at about 12 minutes at
just over 1600 degrees F. Of course the pot's left in longer, as Shelley
says, and some clays require a longer, slower cooling period than others.
Juan recently had difficulty with a new clay until he thought to place a
second, larger sagger over the first, which significantly slowed the cooling

We doubt these will be the "last few years of the ancient methods." The
potters of Mata Ortiz are beginning to catch on to the psychology of their
market, that the process itself has as much enchantment for collectors as
the finished product. They're learning from the experience of the Pueblo
Indians to the north and the Seris to the west.

Here's the crucial problem: How the pot's fired really is important to the
collector market, which is where all the money is. But if you can't tell
whether a pot's been kiln-fired or dung-fired, how will the buyer ever know
what he's getting? The mere suspicion may be enough to kill this market. Is
there any kind of a test? Mike Wisner points out that dung-fired pottery
will usually have a carbon core, but how can that be detected without
breaking the pot? X-ray? Ideas, anyone??

For those not familiar with what's happening in Mata Ortiz, a little over a
hundred miles below the border in northern Chihuahua, Mexico, it is, as
Shelley says, "an astounding miracle of dirt into exquisite pottery." If
anyone is thinking of visiting the village, he/she should see the "Mata
Ortiz Calendar of Events" which we update each month by email. We don't
charge, and it has an encyclopedic amount of information about the village.
Request it at

Spencer and Emalie MacCallum

Shelley wrote:

> The potters of Mata Ortiz, Mexico are running out of their main source of
> fuel, cow manure. The cottonwood trees and scrap are banned and also
>very scarce. Their method of firing is described in several articles in
>Ceramic Monthly archives. Basically, under a clay or tin sagger, left open
2" on
> bottom and top for polychrome/oxidation, and flat to the ground for
> blackware. They pile the dense manure about 6" thick all over, including
>the top. Manure is more even than hardwood. It burns in about 30 minutes.
> Probably it is about 1400 degrees F.
> As a result, several are beginning to use kilns, and museum curators,
>traders and collectors are fearing the market will deteriorate, as has
>with the Native American market. They have experimented with solar but
>cannot get the heat even, nor hot enough long enough. They are
>with some grass mixture. Does anyone have any ideas or experimented along
>this line?
> Any info will be passed along to Juan Quezada. Better yet, go down
>and see for yourself, it is an astounding miracle of dirt into exquisite
> and this may be the last several years of the ancient methods. thanks.