strictly speaking, use of a motor-driven patters wheel is a mechanized method. However, most mechanized clay-forming methods are characterized by much less man al participation than the hand-throwing method just described. These more mechanized methods include jiggering, plastic pressing, and extrusion. Jiggering is an extension of the potters wheel methods, in which hand throwing is replaced by mechanized techniques It is used to produce large numbers of identical items such as houseware plates and bowls. Although there are variations in the tools and methods used, reflecting different levels of automation and refinements to the basic process, a typical sequence is as follows, d picted in Figure 17.6: (1) a wet clay slug is placed on a convex mold, (2) a forming tool is pressed into the slug to provide the initial rough shape-the operation is called barting and the workpiece thus created is called a bar and(3) a heated jigger tool is used to impart the final contoured shape to the product by pressing the profile into the sur face during rotation of the workpart. The reason for heating the tool is to produce steam from the wet clay which prevent sticking. Closely related to jiggering is jolleying, in which the basic mold shape is concave, rather than convex 7]. In both of these processe a rolling tool is sometimes used in place of the nonrotating jigger(or jolley) took this rolls the clay into shape, avoiding the need to first bat the slug