The drawing on the clay having been completed, the next point is to choose the tool best fitted for the work and carefully make the cuts, deepening them from time to time as the work progresses. If the design is to be worked out in line, a chisel, like that illustrated in D (page 285), may be whittled from a pine stick. It is held nearly upright and used as a scraper to cut out at first a shallow channel. Reserve should be exercised in cutting, because, generally speaking, there is danger of making the design too insistent. Some of the best designs are very subtle and quiet. Care should be taken, however, to allow for a slight filling in of the hollow by the glaze when it is applied.
_Modelling a Decoration._--If the decoration is to be modelled it would seem wise to do it, in whole or in part, as the work is built up; but in this case great care will be needed to keep a firm hold on the relief and unity of the decoration. It will be easy to over-model the work.
_How Under-glaze is Applied._--For decoration with under glaze the colours given under the head of glazing (page 304) are mixed in different proportions with dry powdered clay and water to form a colour paste. This is painted on the "green" or moist clay, forming a smooth and even surface. Experience will teach the proportions of colour to be mixed with the clay. These proportions vary greatly with different colours. A very strong colour like cobalt will give a deep blue if mixed in the ratio of one part by weight of cobalt to ten parts of clay. Colours like the oxides of iron and copper are of medium strength, and antimony is quite weak.
Before the work is left to dry it would be well to make sure that all corners and rough edges are smoothed off as they will show light and rough through the glaze. The use of sand-paper, however, is not advised, though it may occasionally be used in the emergency of an accidental roughness remaining after the piece is dry. The aim should be to have all clay work show something of the plastic nature of the material out of which it is made.
_Firing._--Pottery must be "bone" dry before it is fired. A very satisfactory portable kiln for firing may be purchased for from $34 to $175, according to the size. The smallest size, which is illustrated in the next drawing, will be ample for the needs of one or two persons. If, however, the amateur does not care to go to the expense of purchasing a kiln, it is generally possible to find a pottery factory in the vicinity that will undertake the firing and perhaps the glazing.