The rapid appearance and spread of Salado polychrome ceramics across a broad area of the southern Southwest implies the existence of a vigorous Salado trade network.
What Is So Special About Salado White Slip?
The white slip used on Salado polychromes is unique but poorly understood. Patricia Crown in her detailed study of Roosevelt Red Ware, Ceramics and Ideology: Salado Polychrome Pottery, almost completely ignores the white slip as though it were so common as to be unremarkable, she spends at least 3 paragraphs detailing the red slip and speculating on its source and only one paragraph on the white slip. The geography of the Southern Southwest is such that white clay of any sort is extremely rare and most white clays will not turn organic paint black in the firing. So the slip the Salado potters used is rare and of a very specialized type. Anna Shepard understood this slip, in her book Ceramics for the Archaeologist she wrote:
Montmorillonite affects the adsorptive power of clays, which fact suggests that the retention of organic paint by certain clays is explained by the presence of some montmorillonite which holds polar molecules between its units.
As Shepard points out, the secret to turning organic paint black is using smectite clays, of which montmorillonite and bentonite are types. Smectite clays are usually formed from volcanic ash deposits and are know for their absorptive powers. (Weaver 1989)
Some modern Pueblos still make pottery with organic black paint in a way very similar to Salado polychrome, Shepard describes Santo Domingo Pueblo slip thus
cream-colored bentonitic clay. It has higher firing shrinkage than the body and it crazes. Guthe reports that it also becomes gray and in extreme cases even black, but temperature increase alone does not produce this color change. It is probable that some sooting occurs early in firing, and Santo Domingo slip—being highly adsorbent—takes up more carbon and holds it more tenaciously than other clays. Another special, conspicuous defect that occurs either with prolonged firing or in the higher temperature ranges is the burning out of organic paint.
This description matches closely what we find in Salado pottery, the slip is often crazed and some pieces are very dark as though all the carbon was not burned out completely, so the materials must be similar. The special slip used at Santo Domingo and Cochiti Pueblos for making their polychromes has become scarce in recent years, some sources have been lost to development while others are becoming used up. A replacement clay has not been located despite attempts to find one. (Chavarria 2008)
The situation at Santo Domingo and Cochiti Pueblos illustrates just how rare the right type of white clay is that can turn organic paint black. However, because it takes a very small amount of clay to slip a pot, a single clay source could have been traded over long distances and thus supply many villages with enough white slip. It is therefore conceivable that all Salado white slip came from a very few locations and was traded across the southern Southwest by a vigorous trade network.
Tracing The Salado Trade Network
Prehistoric trade networks can be difficult to trace especially if the material traded does not keep well, for example organic material like cotton. Samples of unfired clay have been found by archaeologists in the Southwest many times and yet this white clay slip so commonly used across the Salado world does not show up in the archaeological record. I wonder how well small amounts of smectite clays would maintain its compositional integrity buried in a ruin for several hundred years. Most of the unfired clay identified by archaeologists has been prepared, and tempered clay either in the form of a lump ready to work or a shaped and unfired form, and as such this clay would have its degree of expansion and contraction reduced or “tempered” which is what would tend to break a clay body down over the years as it experienced the natural cycle of wet and dry seasons. The Salado white slip on the other hand would not be tempered and as a smectite clay would possess a high degree of expansiveness, as such I theorize that it would not hold together as a cohesive body when buried in soil, but would actually break down and become integrated into the native soil after a period of time so that when an archaeologist came upon it, it might prove to be just a light colored stain or not noticeable at all. This white clay slip so commonly used by Salado potters has proved difficult to trace archaeologically but we know it was abundantly available because of the volume of pottery produced across a wide area, it must have been a commonly traded item, but if we can’t trace the white clay, what can we use to trace the Salado trade network?
Lithic material is much easier to trace since it does not break down and is easily sourced. Obsidian was rare in much of southeast Arizona before the Salado phenomenon but, almost in tandem with the arrival of Salado polychromes across the region, obsidian becomes very common at the same sites. Much of this obsidian has been sourced to the same location in Mule Creek, New Mexico. (Jones 2012) What connection could there be between these two very different materials that appear in the same locations at around the same time? Both materials are extremely rare in Southeast Arizona, one was used exclusively by men and the other exclusively by women. It is easy to imagine the excitement in a village upon the arrival of a prehistoric trader, it makes good business sense for that trader to bring something desirable for the man and the woman in a household. The appearance of high percentages of Mule Creek obsidian in a Salado site indicates a connection of that site to the Salado trade network, the same network that was presumably transporting the white clay slip.
Sourcing Salado White Slip
It is conceivable then that wherever the sources of Salado white slip are located, that nearby ruins will contain evidence of a strong connection to the Mule Creek obsidian trade. The definitive test for any white slip material will be to chemically compare it to prehistoric Salado sherds, but lacking these test results a strong indicator would also be nearby Salado pueblo ruins with a high percentages of Mule Creek obsidian and Salado polychrome sherds. More on my hunt for the source of Salado white in my next post.
2008 Making Pottery, Seeking Life in A River Apart: The Pottery of Cochiti & Santo Domingo Pueblos, edited by Verzuh, Valerie K.
Museum of New Mexico Press, Santa Fe
Crown, Patricia L.
1994 Ceramics and Ideology: Salado Polychrome Pottery. University of New Mexico Press, Albuquerque.
Jones, Robert M.
2012 Mule Creek Obsidian in the Time of Salado, Archaeology Southwest Magazine Fall 2012 Archaeology Southwest, 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.
Weaver, Charles E.
1989 Clays, Muds, and Shales
Elsevier Science Publishers B.V.. New York, NY