After the decoration is completed there is the process of firing. The chalk-white clay acquires a mellow tint, varied according to the fuel used. Age, and especially daily use over the fire, deepen and beautify this surface tone so that the older a jar, the more delightful is it to possess. In the museum at Santa Fé a large case of jars, all marked as coming from Ácoma, shows that the modern potters are using old designs, often mingled with those believed to have originated at Sía. In earlier days many kinds of fuel were used for the firing process, such as very dry greasewood, sagebrush, or piñon, though wherever cannel coal was found it was given preference. The worst method ever employed was burying the green pot under hot ashes and encircling it with a blazing fire. The better and more usual practice is to dig a little kiln in the ground, or, as is perforce the only way at Ácoma, to hollow out a space in the rock. This is lined with dried cakes of sheep dung—now the universal and almost exclusive fuel in all pueblos. The jars are fitted into this shallow kiln and a dome-like structure of dung is built above, after which the whole is slowly fired. The dung is thought by the Indians to bake the ware more evenly than the resinous woods, but Cushing thinks this fuel so inferior that to its use in great measure can be attributed the deterioration of modern ceramics in the pueblos. Resinous woods cannot be used where the color is the important thing, but the black ware while still hot from a first firing, if coated both outside and in with some of the easily obtained mucilaginous gums, and then burned a second or third time with resinous wood-fuel, is rendered absolutely fireproof, semi-glazed with a black gloss and wonderfully durable. No principle of true glaze is now known to the pueblo potters, but in early days a genuine glaze was used purely for decoration. Being spread over only a part of the surface, it added nothing toward making a jar water-tight. I have found no indication that the Ácomas ever followed any other art than that of pottery, but it is quite possible this may be only their share of the partitioning of the industries agreed upon by the pueblos in comparatively recent time. However, since to-day the sole artistic occupation of the Ácomas appears to be in ceramics, I have omitted, in the consideration of Pueblo arts, both textiles and basketry. With regard to the pottery, Dr. Fewkes says that, in the absence of more definite insight, Ácoma pottery bears little resemblance to that peculiar to southern clans; it is distinctly Queresan, and resembles more closely the pottery of ancient Hopi than that of ancient Zuñi, or of Little Colorado ware—by which it does not seem to have been affected.[262]