Andy Ward Pottery
traditional SW pottery

How Was Prehistoric Salado Polychrome Pottery Fired?

Very few prehistoric kilns have been identified in the southern Southwest (Sullivan 1988) and none in association with Salado ceramics. In looking for clues to how the Salado fired pottery we can attempt to trace the technology backwards, so the first question we must ask is, where did this technology come from?

Origins of Oxidized Organic Paint Pottery Technology

Wingate Black on Red, a predecessor of Pinto Polychrome uses "Oxidized Organic Paint" technology.

Figure 1. Wingate Black on Red, a predecessor of Pinto Polychrome uses “Oxidized Organic Paint” technology.

Some have linked Salado polychrome pottery to Kayenta pottery, specifically Tusayan White Ware (Crown 1994, Lyons 2003) and when examining Salado design motifs and Salado material culture (architecture and perforated plates) that connection makes sense. But when examining Salado polychrome from a technological standpoint, that connection breaks down because while the Kayenta did have a tradition of organic paint pottery, they have no tradition of oxidized organic paint pottery (Crown 1994, Lyons 2012) which has very different and specific requirements when compared to reduced, organic paint white ware like Tusayan White. So the question we must ask is, was the firing regime used by the Salado new or borrowed? Cibola potters had been making oxidized organic paint pottery (Wingate Black-on-Red, Saint Johns Polychrome and related types) (Figure 1) for over 200 years when Salado polychromes first appeared around 1280. (Neuzil and Lyons 2005) And while the design motifs found on Salado polychromes bear the influence of Kayenta/Tusayan designs, the same change to “Pinedale Style” occurred in White Mountain Red Ware at around the same time that Pinto Polychrome appears on the scene. In fact White Mountain Red Wares are commonly found in early Salado and pre-Salado sites across the region, (Clark 2001, Johnson and Thompson 1963) suggesting that this type played a key role in the development of Salado polychromes so if the potters in these sites were not already making oxidized organic paint pottery, they were at least in contact with people who were. The creation of any organic paint pottery is dependent on the confluence of two key items, 1) the right type of smectite clay slip that will hold organic paint and 2) the technology to make and fire that pottery in such a way that the paint turns black. Therefore in the development of Salado polychromes it would appear that the firing technology probably came from the Cibola region with the discovery of the white slip being the key new development that led to the creation of this new type of pottery.

Figure 8. Some Salado polychrome sherds illustrating the nearly ubiquitous carbon core and thin oxidized rind. (Photo by the author)

Figure 2. Some Salado polychrome sherds illustrating the nearly ubiquitous carbon core and thin oxidized rind. (Photo by the author)

What The Sherds Tell Us

Unfortunately we know as much about White Mountain Red Ware potter firings as we do about Salado firings, very little. What then can we learn from the sherds about the firing process? Most Salado polychrome sherds have a dark carbon core, (Figure 2) that carbon can tells us something about how it was fired. Carbon commonly accumulates on the surface of pottery during the early stages of an outdoor wood firing also any organic material inside the clay body will also carbonize, all this carbon will produce dark grey and black colors but will begin to burn out in the later stages of the firing when oxygen is more abundant. (Shepard 1985) Looking at cross sections of Salado polychrome sherds reveals that the burning out of carbon has usually occurred only in a thin rind on the outside of the pottery, this indicates that the oxidation stage of the firing is extremely short. Refiring tests have shown that most Salado polychrome was fired above 600 C and below 800 C. (Crown 1994) All this information, taken together paints a picture of a low temperature, short duration firing with an abbreviated oxidation period.

Pottery firings are often over-simplified by speaking of them as either oxidizing, reducing or neutral, the truth is that all outdoor firings have at least two important stages, the first stage takes place while the fuel is actively burning and giving off gases in which the pottery is in a neutral atmosphere with a shortage of oxygen and an abundance of carbon. This is the stage in which the surface of the pot will absorb carbon from the atmosphere. Once the fuel stops actively burning and begins turning into coals, the fuel stops putting off gasses and the pottery is in an oxidizing atmosphere characterized by abundant oxygen and little free carbon. At this point the carbon will start burning off as long as the temperature remains high enough, > 700 C. (Shepard 1985) So what we have learned by examining the sherds is that to fire Salado pottery authentically we must maintain an oxygen-poor, carbon-rich environment in the first stage of the firing, then keep the oxidation phase as short as possible, allowing enough time to clear up the surface of the pottery but not so much that it burns the carbon out of the core or burns the organic paint away.

Historical Precedence

Anna Shepard captured temperature curves for various potters for her book Ceramics for the Archaeologist, the Cochiti potters represented in her data were firing oxidized organic paint pottery, technologically similar to Salado polychrome. (Figure 3) The temperature curves for the two Cochiti pottery firings that she recorded is similar to what the sherds indicated we need to fire Salado polychromes, that is, low temperature, short duration with an abbreviated oxidation period. In the Cochiti firings the temperature readings stop near the top of the temperature peak, this is because the potters are actually removing the pottery from the fire soon after the oxidation phase begins, while the pottery is between 670 and 715 C thereby stopping the oxidization of the pottery. (Shepard 1985) Of course these Pueblo potters are using dung for fuel, a luxury not available to the Salado, so although we can learn from these Cochiti firings, we cannot imitate them exactly.

Figure 9. Shows the brief oxidizing period used for Cochiti oxidized organic paint pottery. Temperature Curves for Firing of Oxidized Ware, Ceramics for the Archaeologist, Anna O. Shepard.

Figure 3. Shows the brief oxidizing period used for Cochiti oxidized organic paint pottery. Temperature Curves of Firing of Oxidized Ware, Ceramics for the Archaeologist, Anna O. Shepard.

In my next post I will show how I have used the clues found in Salado sherds and Shepard’s data to successfully recreate the correct firing environment for authentic Salado pottery replicas.

References Cited

Clark, Jeffery J
2001 Tracking Prehistoric Migrations: Pueblo Settlers Among the Tonto Basin Hohokam University of Arizona Press, Tucson

Crown, Patricia L.
1994 Ceramics and Ideology: Salado Polychrome Pottery. University of New Mexico Press, Albuquerque.

Johnson, Alfred E. and Thompson, Raymond H.
1963 Artifact Descriptions and Proveniences for the Ringo Site, Southeast Arizona
Archives of Archaeology Number 22, Arizona State Museum and Department of Anthropology, The University of Arizona, Tucson

Lyons, Patrick D.
Maverick Mountain Series and Roosevelt Red Ware Origins
Online exclusive essay for Archaeology Southwest Magazine Vol. 26, Nos. 3 & 4 (Summer and Fall, 2012), Archaeology Southwest, Tucson

Lyons, Patrick D.
2003 Ancestral Hopi Migrations
University of Arizona Press, Tucson

Neuzil, Anna A. and Patrick D. Lyons
2005 An Analysis of Whole Vessels from the Mills Collection Curated at Eastern Arizona College, Thatcher, Arizona. Technical Report No. 2005-001. Center for Desert Archaeology, Tucson.

Shepard, Anna O.
1985 Ceramics for the Archaeologist. Reprinted. Braun Brumfield, Ann Arbor. Originally published 1956 [revised 1965], Carnegie Institution Publication 609. Washington, D.C.

Sullivan, Allen P. III
Prehistoric Southwestern Ceramic Manufacture: The Limitations of Current Evidence American Antiquities, 53(1), 1988

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About Andy Ward

I am an independent researcher, writer and artist interested in all things Southwestern. Southeast Arizona is my home and area of primary interest.

2 thoughts on “How Was Prehistoric Salado Polychrome Pottery Fired?”

  1. Clint Swink says:

    Andy, I think your opinion is off a bit. The carbon in the atmosphere remains the same, only the oxygen changes when one leaves the iron to combine with the carbon in the reducing gases of the atmosphere. I think you are confusing hydrocarbons (smoke) with CO2 and CO carbon.

  2. Andy Ward says:

    Clint, it seems we often speak different languages when discussing firing and you certainly have the edge on me when it comes to chemistry. My background is fire science which is a little weak on chemistry but strong on the process of combustion.

    To quote Anna Shepard “Not infrequently when there is insufficient draft, the fuel will give off smoke containing colloidal carbon, which will cause sooting or smudging of the pottery.” (Ceramics for the Archaeologist page 216) This is the carbon I am referring to.

    “If oxidation is incomplete, a gray core usually marks a carbonaceous clay, but there is always the possibility that a paste was smudged at some stage of firing. It is advisable therefore to determine the ease of oxidation, since the lightly held carbon from a smoky fire burns out at a lower temperature than most carbonaceous matter” (Ceramics for the Archaeologist page 105)

    You and I disagree about the source of the carbon in a carbon core, however I contend that at least in the case of most Salado polychrome pottery, carbon in the atmosphere is the source of that carbon and I think Shepard supports this theory. This is an area where some experiments could prove valuable in clearing things up. I can say that I have been able to obtain a pure black carbon core in a non-carbonaceous clay body which I believe lends credence to my theory.

    Black carbon core in a mineral clay.

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