The roof or vault of the oven is then built. Some potters place iron bars across the top of the dung-ring, keeping them from touching the vessels by inserting tin cans and stones. On these bars flat cakes of dung are laid, and the larger holes are covered with smaller pieces of dung. Other potters dispense with the bars and rest a large circular cake of dung upon cans and stones set in the centre of the pile of pottery. The space between this central cake and the top of the dung-ring is bridged by other cakes which rest on the dung alone. In this manner a low vault of dung-slabs is formed, roughly square in shape, two and a half to three feet on a side, and about a foot and a half high ([pl. 25], c). There are still left numerous spaces, both large and small, between the cakes. These are covered with smaller pieces of dung, and with old tin tops of lard-pails or discarded tin plates ([pl. 26], a). Even after this, however, there remain enough small spaces to allow free circulation of air, and to prevent the smothering and consequent smoking of the vessels. Through these smaller spaces the flames and pots may be seen. The building of the oven is now complete; by this time the fire has usually been started, and the flames are well under way.
As a rule more than one burning is undertaken during a morning. The building of the oven for the second burning differs slightly in its preliminary stages from that described above. After the previous oven has been destroyed, the ashes are smoothed out, and the grate set straight and carefully dusted so that no ashes remain ([pl. 26], b). The bowls are than placed on it as before. Partly burned cakes of dung, which remain from the first burning, are re-used. If, in placing them on the oven, ashes drop on the vessels, care is taken to blow them off.
Some potters stand the vessels which are to be burned on the warm cakes of dung for a few minutes before placing them on the grate ([pl. 26], b), a process which is supposed to heat them slightly and thus prevent breakage during firing. Other potters would not think of doing this, for vessels treated in this manner always have discolored bases, where the warm dung has touched them.
Ollas twelve to fourteen inches in diameter are burned in pairs, with a few smaller pieces beside them. The oven is built in the same manner as before. Very large ollas are usually fired one at a time; the oven, except for its greater size, is said to be of the usual type.
Burning
As was said above, the firing of the pottery is done in the morning. The Indians say that they wish to get it over with “before the sun grows hot”. Their own personal comfort probably plays a more important part in this than does the effect of the sun upon the pottery. As a rule the firing is withheld until a sufficient number of finished vessels have accumulated to permit three or four burnings in one morning. The entire forenoon is spent at this work, and sometimes it drags over until early afternoon. The actual burning of the vessels occupies a period of about half-an-hour for each oven; it is said that the length of time has not been appreciably shortened in the past forty or fifty years. The black ware is always saved for the last oven, since the process employed completely precludes the possibility of rebuilding the oven at once.
At the beginning of the burning white smoke is apt to be given off, but too much smoke is regarded as a bad sign, since it signifies that the dung cakes are not sufficiently dried. After fifteen minutes or so, that is when the process is about half finished, the amount of smoke has greatly diminished ([pl. 26], a). About this time more kindling is added through openings made by temporarily removing a piece of tin, and new cakes of dung are added where necessary, usually on the top of the oven.
The Indians say that they judge of the condition of the pottery in the oven by its color; the paste and slip must be of just the proper shade before the vessels are
PLATE 25