Surface Treatments

After the vessel had been formed, it was allowed to dry for several days. A final treatment was given to the surface before the vessel was painted and fired.

Plain and Painted Wares

In some cases, this simply involved smoothing with a gourd rind or simple tool. More elaborate pottery might be polished with a stone, giving it a glossier finish. If an even finer surface was required, or if a specific color which differed from the clay paste color was desired, a slip was added. A slip is a highly diluted clay wash, made from better clays with known firing properties. The most common slip colors were white and red, each made from different clays which reacted differently to the firing process.


Some vessels seem to have been left unfinished. The result was a rather irregular surface from which temper protrudes, giving the vessel a rough finish.


The surface of most vessels was at least smoothed, either with a gourd rind or some other kind of tool. On many sites, pottery fragments, or worked sherds, were used in the smoothing process. These tools are recognizable because their edges show signs of shaping, as along the lower edge of the sherd shown at the upper left. Smoothing gives the vessels a flat, matte finish, but one that lacks lustre.


To achieve a lustrous, reflective surface, a vessel was polished. This was done using a smooth river stone such as the one shown at left. A good polishing stone was highly prized, and might be passed from mother to daughter. The polishing process could bring up the sheen of a plainware vessel, but was more effective on those which had a fine slip, like the San Francisco Red vessel shown here.


By controlling the firing conditions, potters were able to convert certain minerals in the clay of interior slips to a black color. This "smudging" was often polished to a lustrous finish, as seen in the example here.


Some of the earliest attempts at providing slips to vessels were less than successful. Slips did not adhere well to the walls of the vessel under the low firing temperatures that were employed at that time. The slips would then rub or wash off over time. The only evidence of these is a ghostly red cast to the surface of some of these vessels.


Potters eventually learned that by adding a wash of highly diluted, fine-grained clay to the surface of the vessel, a higher polish could be achieved, as in the San Francisco Red vessel above. By adjusting the slip material and firing technique, white slips could be achieved. These could then be painted with black or red designs. In this example, the original vessel color is visible along the rim.

Corrugated Wares

In many vessels, particularly the daily-use vessels such as cookware, the exterior surface of the coils was never smoothed, leaving corrugations. This was probably to improve the manageability of these vessels, as in many cases they are only corrugated where they would be picked up. There were, however, a number of ways these corrugations could be visually enhanced.


Vessels whose corrugations have no additional treatment are called plain corrugated. Coils range from about a centimeter wide to extremely narrow, as in this example.


Quite often only the necks of jars were left corrugated, while the remainder of the vessel was smoothed. Two mathods were used to achieve this. If the coils are simply rings stacked one on top of the next, the vessels is termed neck banded. If the coils spiral up around the neck, as in the example here, they are called neck corrugated.


Sometimes neck corrugations were enhanced by the addition of incised decoration. A sharp tool would be drawn through the wet clay, creating patterns that complemented the natural pattern of the corrugations.


Another way of introducing more visual interest in the coils was by punching rows of dots into the wet clay with a sharp tool.


In many of the later vessels, the corrugations have been indented. This was usually done with the finger, and is sometimes refered to as finger- indented. This treatment not only gave the vessel an interesting, rippling surface, but may have helped to bind together the coils more effectively.


By combining plain and indented corrugations, interesting patterns could be achieved. Sometimes bands of indented and plain corrugations would alternate up the vessel. In the example here, a diamond pattern has been indented into an otherwise plain corrugated vessel.


The fillet rim is perhaps the bowl's version of neck corrugation. To a plain, smudged bowl, two or three rows of indented corrugation were provided near the rim.