Andy Ward
traditional SW pottery

How Was Prehistoric Salado Polychrome Pottery Fired?

There is no way for anyone today to say for sure how the ancient Salado potters fired their polychrome pottery, that part of the technology was lost when the Salado moved away and no longer had access to the specialized slip material. In trying to follow the Salado road backwards I have run down many dead ends and wandered lost in the wilderness that is Southwest prehistory. I once thought that the sherds held clues to the way the pottery was fired, now years later having successfully produced authentic looking Salado polychrome pottery, I’m not so sure they do.

The most difficult part of the puzzle of Salado polychromes is that it is a two part problem, requiring a unique slip material and a specialized firing procedure, if either one of these elements is wrong it is impossible to solve the problem correctly. I started looking for the white Salado slip when I was still a teenager, it was then that I realized how rare white clay of any kind was in the Salado homeland. It was not mere chance that white pottery had been rarely produced in the southern Southwest before Salado, it was the geologic hand that nature had dealt that region, one with lots of browns and red clays and very few white clays. Up until 2014 I had sampled a range of light colored clays from across the southern Southwest none of which did both of the things the Salado slip needed to do; turn organic paint black and stay reasonably white in the firing. It was then that I decided to try using the smectite clay slip that was being successfully used by Anasazi pottery replicators, after all it did the same things the Salado slip needed to do, it turned organic paint black and stayed white.

slightly over-oxidized pots slipped with the Colorado smectite clay

slightly over-oxidized pots slipped with the Colorado smectite clay

With one part of the puzzle seemingly in place, that is the special white slip, I entered my first rat-hole. Although I knew that Salado potters did not have access to this slip from southwest Colorado, I was convinced that the Salado slip must have been chemically very similar to it, with this “fact” firmly in hand I began trying to solve the second piece of the puzzle, how to fire Salado polychrome. My Anasazi replicator friends fired in pits that were smothered, this could not have been the Salado way because the reds would not mature to the bright reds that Salado polychromes are famous for. The next obstacle was that if I oxidized the pottery enough to make the reds bright I usually burned off much of the organic paint, after much experimentation and talking to an experienced Anasazi replicator friend of mine I developed a method of firing my Colorado smectite clay slip with an abbreviated oxidation period, breaking the fire down and stopping the firing very early in the oxidation phase. This resulted in marginal acceptable results about half of the time, producing either over-oxidized grey paint or dark smudgy under-oxidized pots the rest of the time, I kept experimenting to try to get the timing right but it was extremely difficult to do. This broke one of the rules I had set to guide my Salado polychrome research, the process had to be simple, in order for Salado pottery technology to spread quickly and widely across the southern Southwest it had to be dead-simple, something you could show someone once and they could get it and repeat it.

There were other rat-holes along the way too, like Rod Swenson’s “non-smothering paradigm” which cost me about six months of research and was a total dead end, (having talked with many of the best pottery replicators about this method I have yet to find anyone who has been successful with Rod’s approach). There was also the Benson white clay rat-hole and the grass firing rat-hole to name a few, suffice it to say I followed every possible approach I could think of and followed those ideas as far as they would take me before back-tracking.

slightly under oxidized (left) and slightly over oxidized (right) pots slipped with the Klondyke zeolite

slightly under oxidized (left) and slightly over oxidized (right) pots slipped with the Klondyke zeolite

In the fall of 2015 I located a large deposit of white material near Klondyke, Arizona very near to the geographic center of the Salado phenomenon, it wasn’t exactly clay, but it could be refined and applied as a slip and it fired hard and white, even better it held onto organic paint tenaciously, producing a good black. The material turned out to be zeolite, a relative of smectite (they are both produced from volcanic ash deposits in water) and it had very different working properties from any slip I had tried before so it took me some time to figure out how to apply and smooth it to produce a texture like that found on Salado polychrome pottery. Remember that there are two parts to this puzzle, the slip and the firing, now that I had found a decent slip I was way off base with the firing which made it hard to recognize the value of this slip. When I fired the Klondyke slip I used the abbreviated oxidation method I had developed for the Colorado smectite clay slip, the results of this were most often dark smudgy pots that were inadequately oxidized because the Klondyke slip has a strong affinity to carbon and will aggressively absorb it from the atmosphere in the early stages of the firing. I came to the conclusion that the firing needed to be more open and oxygen rich to prevent this buildup of carbon but a typical open oxidizing firing resulted in the organic paint getting burned off the pot. These failures combined with the difficulty I was having with the surface finish led me to abandon the Klondyke slip after the Kiln Conference of 2016.

Then Clint Swink, the well know Mesa Verde black on white replicator, did some refiring experiments with Salado polychrome sherds and told me about their remarkable ability to hold onto their organic paint even when oxidized in an electric kiln. In the spring of 2017 I visited Clint’s studio in Colorado and looked at his refired Salado sherds under his microscope, the electric kiln had burned all the carbon out of the clay body (the “carbon core”) yet the organic paint had stayed black. What was going on? Were they using some kind of mineral paint or a mineral/organic hybrid? Driving back home from Durango I was not sure what to make of Clint’s findings, I ruminated on it all summer long. In the fall, when I typically begin a new season of Salado polychrome experimentation and research, it occurred to me that if the Salado white slip can keep organic paint black through an extended oxidation period, perhaps that is what the Klondyke slip needs to clear up the surface, a longer oxidation period. I decided to refire a few of the smudgy misfired pots I had made with the Klondyke slip in order to let them oxidize for a longer time. The pots spent over 20 minutes at 750 C at the end of the firing which was enough to burn all the extra carbon from the surface of the pots, yet the organic paint was a good dark black. It appeared that the Klondyke slip has similar properties to the prehistoric Salado slip, that it can hold onto organic paint even in a long hot oxidation.

properly oxidized pottery resulting in a clean white slip and black painted areas. Klondyke slip

properly oxidized pottery resulting in a clean white slip and black painted areas. Klondyke slip

A few more months of experimentation filled in the remaining gaps in my process. The firing could not be wide open, like what might be used to produce red on brown pottery, the atmosphere needed to be very closed at the beginning of the firing process, resulting in a carbon rich, oxygen poor atmosphere around the pot, this would prevent the fire from burning off the organic paint before it was set in the slip. Somewhere in the range of 500 to 600 C the carbon was locked into the slip, after that the atmosphere can be open and oxidizing which will burn out any carbon the slip absorbed in the early stages of the firing. By stacking the wood around the pottery very closely then filling or covering any sizable gaps at the bottom with slabs of bark, the early stages of the firing can be kept oxygen poor, then as the fuel is consumed it naturally opens itself up as the temps increase allowing more oxygen in, at this later stage I remove the bits of bark which are always the last to combust anyway.

a good hot soak, 750 C for 20 minutes

a good hot soak, 750 C for 20 minutes

Here is my step by step process, the key elements to remember are; 1. carbon rich, oxygen poor atmosphere in the early stages, 2. hot, oxygen rich atmosphere in the later stages.

  1. Build a “primary fire” to create a bed of coals and to preheat the pots and “kiln furniture” (stones) in.
  2. Stack kiln furniture on top of coals and pots upside down on kiln furniture. Surround pottery with cover sherds, preventing fuel from coming into contact with painted areas.
  3. Stack wood tightly teepee style over the pottery. Fuel should be of a size easily breakable by hand or foot, no bigger in diameter than your arm. Sticks should be laid at such an angle that they will not fall over as they burn but will lie on top of the pottery, leaving a heap of coals covering the pots.
  4. Fill in or cover remaining gaps at the bottom of the fuel stack with bark slabs.
  5. Light the “secondary fire” and monitor closely, adding fuel to any areas that are burning away faster than the rest. The goal is to get the fire to burn to coals evenly, at the same time all the way around.
  6. Let the fire burn down to coals, allow the pots to soak under the layer of coals until the fire begins to burn to ash and cool, then begin to carefully and gently rake away coals and remove cover sherds. Allow the pots to cool slowly before removing.

I can’t say that this is the way the prehistoric Salado potters fired their pottery because we currently have little or no evidence of how they fired. What I can say is that this method produces good results using a material that has similar properties to the material used by Salado potters. I am open to any suggestions and improvements in this process that others may suggest.

 

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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:

    Very good Andy. Glad to hear you are on this new, strong path and enjoying success. I am surprised you are using cover sherds, but think it is a good addition. Best wishes for continued firing findings.

  2. Andy Ward says:

    Thanks Clint, you have been an inspiration and a fount of information for me.

    I’m not sure that I need the cover sherds but I have a hunch that they are needed to protect the paint from direct flame contact in the early stages of the firing. I need to do more experimenting to find out for sure. I’ve never been completely anti cover sherd, it is safe to assume that the Salado were at least familiar with their use as their other Mogollon neighbors in the White Mountain and Casas Grandes regions were definitely using them.

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