While Charlie was finishing his firing Bill Lucius prepared a small slab-lined pit for a firing black-on-red pottery. Following the preheating of pots outside of the pit, cold sandstone slabs were placed on the resulting coals, onto which the pots were arranged and allowed to continue heating. Subsequently small splits of juniper kindling were laid among the pots, which in retrospect was an error since when they ignited they created hot spots that caused spalling and cracking. The firing continued with the stacking of a substantial amount of juniper fuel across the slabs, which was allowed to burn down, creating a reducing covering over the pottery. Upon opening the pit it became apparent that the firing was too hot (the pyrometer recorded a temperature of almost 1000 degrees Celcius), for too long and further was too reducing for the various Morrison Formation red clays to tolerate. Many pots were vitrified almost to the point of being glassy and the surfaces came out dark brown to black, which obscured the painted iron and manganese designs. Suprisingly, several gray body clays with red slip and iron paint tolerated the conditions and came out with black designs! Although the excessive heat burned off the red slip, where protected by the paint it must have interacted with the iron and beeweed to produce the mineral paint observed on prehistoric Black-on-white pottery. So now we kow that mineral paint must require the addition of red clay to come out black when painted on a gray or white body clay, otherwise the iron and beeweed paint consistently comes out brown or red. As always, we continue to learn from our mistakes!
Meanwhile Tim Wilcox began setting up his Modern Hopi Style firing by preheating pots around a warming fire (no pit). In this case Tim placed a layer of broken pottery sherds as kiln furniture, onto which the pots were placed. A carefully interlaced covering of roofing tin was then added and covered with coal, bricks of sheep dung and a few pieces of juniper. The whole affair reignited itself and was allowed to burn down slowly. The tin gradually reappeared and when the kiln was opened sometime later it revealed oxidized, well-fired pottery with typical warm tones and blushes. Well done!
Almost simultaneously JoAnn Weldon and Wayne Keene started two different smudge firings, which involved covering the unfired pot (JoAnn’s pot in lower left of Wayne”s two bowls) with a metal container, which rests on a bed of coals formed by the warming fire. A teepee of juniper fuel was subsequently stacked over the container and allowed to burn furiously. After the flames had consumed most of the fuel the fires were smothered with powdered horse manure, which effectively saturated the atmosphere with free carbon. The carbon impregnated the clay bodies, resulting in matte paint designs on glossy, stone polished surfaces.
Following Rick’s approach, we began firing the Black-on-white kiln in the late afternoon in the hopes of letting the wind subside, which can result in uneven kin temperatures, and to better gauge the firing progress by flame color. As the sun was sinking low we filled the slab-lined pit with copious amounts of juniper fuel to create a thick bed of coals. The amount of wood consumed in this first step was considerable, resulting in a bed of coals approximately 8” deep over the bottom slabs used to line the pit. The painted pots were brought out and set around the outside of the pit to preheat and Charlie performed his traditional blessing of the pots and potters with corn meal.
When the fuel had burned down to coals a loosely spaced bed of cold sandstone slabs was put down over the coals onto which the pots were carefully stacked (note the red hot coals in front of the pots in the photo below right). The closed forms went on first (base down) and bowls were inverted over them, which prevents them from accumulating charcoal and smudging the interior. No cover sherds were used to cover the pots as Rick 's experience is that they are superflous in a properly fired trench kiln.
A pat of large cones was centrally placed with a sherd hood in order to record the effective temperature of the firing. Rather than immediately proceed with the firing, the pots were allowed to slowly accumulate heat from the coals below (about an hour). As explained by Rick in his introductory lecture, this slow water-smoking period is essential since it ensures the remaining free water as well as the chemical water in the clay body is safely driven out of the pots. Rick’s approach to stacking the fuel over the pots was an example of a potter’s intuitive approach. Using the upright slabs as well as stone bulwarks on either end of the kiln as supports, he began cribbing long branches of juniper into a loose framework above the pots. When the cribbing reached waist high he instructed helpers to start an ancillary fire nearby, upon which he had the helpers place other branches across so that they would ignite in the middle of their lengths. When they had ignited they were lifted on top of the cribbing and allowed to continue burning. Slowly the flames spread to the supporting cribbing of wood.
This action created an updraft, which pulled the hot air from the coals up through the pots and into the air. As the branches burned through, their weight pulled the unburned ends down, preventing them from falling onto the fragile pots and instead formed a simple tent structure that only dropped small embers into the firing chamber. The fire was stoked by adding to the cribbing until the pit was covered by a raging inferno of flames. Again, the amount of fuel used in the firing was considerable, and Rick would have used more if any more were available. A final addition of recently dead pinyon branches resulted in a blaze of heat and light. As the fire burned down we observed distinct blue flames indicative of high temperatures dancing over the top of the burning mass of coals. Despite the amount of sparks being given off by the firing and the continued gusty winds that we had hoped to avoid by firing at night, we managed not to start any of the surrounding trees on fire. After watching the coals awhile we left the kiln to cool down overnight and went to bed.
The next morning we were greeted with the sight of extensive white ash with occasional exposed pottery mouths and vessel walls. It was readily apparent that the overnight wind gusts had kept the embers burning, resulting in oxidation observable as light orange blushes on exposed vessels. Indeed, the exposed sandstone slabs of the kiln were distinctly orange from the oxidation. And glowing red coals could still be discerned under the ash covering. Although we should have waited another day for the pit to cool, we began a slow, methodical unloading of
the kiln.
After loosing one piece due to dunting in the cool breeze, we adopted the practice of merely lifting the pots out of the pit onto the still quite warm ash, allowing them to cool slowly. A short time later Rick arrived and the process of taking the kiln apart and discussion of the firing successes and failures continued until all pieces were recovered and removed from the pit.