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 ROMANO-BRITISH NORTHAMPTONSHIRE rarer, are painted in artistic fashion — such as two fragments, now in Dr. Walker's collection, on the copper-coloured surfaces of which the potter has gracefully depicted in white and yellow a man's head with a peaked cap, and an arm holding a small axe. But these vessels painted in white, whatever their type, are less frequent and less characteristic than the thumb vases and vessels decorated in self-colour slip which seem to be the most typical Castor wares. ^ Mr. Artis has printed some interesting details as to the method by which these wares were baked, coloured, glazed and ornamented in slip, which it will be best to repeat in his own words. As to the baking — The kilns (he says) were first carefully loose-packed with the articles to be fired, up to the height of the side walls. The circumference of the bulk was then gradually diminished, and finished in the shape of a dome. As this arrangement progressed, an attendant seems to have followed the packer and thinly covered a layer of pots with coarse hay or grass. He then took some thin clay, the size of his hand, and laid it flat on the grass upon the vessels ; he then placed more grass on the edge of the clay just laid on, and then more clay, and so on until he had completed the circle. By this time the packer would have raised another tier of pots, the plasterer following as before, hanging the grass over the top edge of the last layer of plasters, until he had reached the top, in which a small aperture was left, and the clay nipt round the edge ; another coating would be laid on as before described. Gravel or loam was then thrown up against the side wall where the clay wrappers were commenced, probably to secure the bricks and the clay coating. The kiln was then fired with wood. In consequence of the care taken to place grass between the edges of the wrappers, they could be unpacked in the same size pieces as when laid on in a plastic state, and thus the danger in breaking the coat to obtain the contents of the kiln could be obviated. The slate blue or copper colour on the outside of the ' Castor ware ' seems to have been produced generally by a trick in the process of baking, and not by a varnish. During an examinatioii of the pigments used by the Roman potters of the place, I was led to the conclusion that the blue and slate-coloured vessels met with here in such abundance, were coloured by suffocating the fire of the kiln, at the time when its contents had acquired a degree of heat sufficient to insure uniformity of colour. I had so firmly made up my mind upon the process of manufacturing and firing this peculiar kind of earthenware, that, for some time previous to the recent discovery, I had denominated the kilns in which it had been fired, smother kilns. . . . The mouth of the furnace and top of the kiln were no doubt stopped ; thus we find every part of the kiln, from the inside wall to the earth on the outside, and every part of the clay wrappers of the dome, penetrated with colouring exhalation. As further proof that the colour of the ware was imparted by firing, I collected the clays of the neighbour- hood, including specimens from the immediate vicinity of the smother kilns. In colour, some of these clays resembled the ware after firing, and some were darker. I submitted them to a process similar to that I have described. The clays, dug near the kilns, whitened in firing, probably from being bituminous. I also put some frag- ments of the blue pottery into the kiln ; they came out precisely of the same colour as the clay fired with them, which had been taken from the site of the kilns. The experiment proved to me that the colour could not be attributed to any metallic oxide, either existing in the clay, or applied externally ; and this conclusion is confirmed by the appearance of the clay wrappers of the dome of the kiln. It should be remarked that this colour is so volatile, that it is expelled by a second firing in an open kiln. above the ' thumb vase ' and of the ' barbotine ' method of ornamentation. Both seem to occur occasionally in Italy and the Mediterranean lands, but neither is common enough to form a definite precedent, such as the red Arretine ware forms for the west-European ' Samian.' 209
 * It would be interesting, but I have not found it possible, to trace the origin of the shape called