Firing Pottery

Now that all the preparations were complete, the vessel was ready for firing.


Firing Techniques

Unlike today, kilns were not available, and pottery was usually fired in pits. Fuel was placed in the bottom of the pit, then the dried pottery was carefully stacked above it. The vessels were surrounded with old broken pottery to protect it from the flames and then covered with more fuel to create a smoldering mound. Several factors determined the success or outcome of the firing process.

REDUCING ATMOSPHERE

In most cases, efforts were made to control the amount of oxygen that entered the firing chamber. This is called a reducing atmosphere. A reducing atmosphere was necessary in black-on-white pottery to prevent minerals in the slips and paints from oxidizing and changing color.

ACCIDENTAL OXIDATION

Accidental localized exposure to oxygen might change a part of the black paint to red, as can be seen in many of our examples from the Mimbres site at Mattocks.

LATE OXIDIZING ATMOSPHERE

The Mimbres may have recognized the potential of these accidents, as they developed fine red-on- white wares, in which the designs and pigments were clearly deliberately oxidized. This had to occur late in the firing process, so that the whites do not also turn red.

OXIDIZING ATMOSPHERE

An oxidizing atmosphere is one in which oxygen is allowed to enter the firing chamber. An oxidizing atmosphere was particularly desirable with the red wares, as the slip ultimately obtained its rich red color when iron in the clay literally rusted.

FIRE CLOUDS

If vessels were not properly protected from the flames by broken pottery, fire clouds would appear on the surface. 

WARPING

Warping can be caused by a number of factors - improper loading of the pottery in the firing pit and inadequate temper are probably the most prevalent. This warping does not make the vessel unusable, and unless the damage was extreme, the amount of effort put forward to create it must have outweighed the disappointment.