The following outline describes some of the better known forming techniques and the physical attributes normally correlated with them.
Ro lls or " c o i l s " o f uniform thickness are produced hy rolling clay horizontally on a Hat surface or vertically between the hands. Diameters of coils range from 5 to 10 mm for thin-walled vessels (wall thickness less than about 5 mm) to 5 cm or more for large vessels with wall thicknesses of 2 to 3 cm. In general, coil diameter is about double the wall thick ness. Length may range from about 10 cm to one me ter. The longer the coil, the more skill is needed to produce it with a uniform diameter.
Building up a vessel with coils is accomplished by placing them around the circumference and gradually increasing the height d igs. 42. -4K). This produces a ridged and grooved surface, which is evened by scrap ing and smoothing. A variant of this technique is known as "ring building." Coiling involves a spiral, whereas ring building involves laying a series of circu lar coils on top of one another. Since essentially the same procedures are required and the possibility of distinguishing them in archeological ceramics is re mote. 1 recommend that the term "lin g building" be avoided or used as a synonym for coiling.
Coiling is essentially a primary forming technique, meaning that it is used to produce the overall shape of a vessel that is refined by other techniques. Coiling can be combined with other primary techniques. I'or example, the lower part of a vessel may be thrown on a wheel or pinched and the upper part completed by adding one or more coils (Figs. 12. 66).
The following attributes are associated with coil ing (Fig. 4‘)):
Surface Markings. Usually none, unless the coils have not been obliterated by subsequent finishing.
Surface Finish. See surface markings.
Su rfa ce D eposits and Segregation Effects.
Usually none.
Variations in Wall Thickness. Invariably present. Walls may be twice as thick at some points as at
Fig. 48. Forming a vessel by co iling. The lowest coils are supported in a half coconut shell, which rests on a ring of coconut fiber. The potter is obliterating the joins between the coils on the interior. Mailu Island, Papua New Guinea (cf. Fig. 42 a).
others. Regular ‘"corrugations” will be evident if the junctions were not obliterated. (Irregular or random variations in thickness usually result from later finish ing operations, such as scraping and smoothing.)
Fracture. Sherd edges irregular, with meandering contour. Fdge tends to break into more or less "c u b ic " facets if the clay body was very fine grained. Occasionally, a step-like fracture occurs. If joined
Fig. 52. Forming a small bowl by pinching.
Pinching
This is probably the simplest technique. It in volves squeezing clay between lingers and thumb or between the lingers of opposing hands. I he walls can be thinned and increased in height by repeating this action rhythmically at closely spaced intervals as the vessel is revolved. Small vessels can be revolved in the hand: larger forms are usually placed on a turntable. Although small vessels may be formed completely (Fig. 52). pinching is normally used to begin the base (especially rounded bases) or as a finishing technique for reducing gross variations in wall thickness, espe cially near the rim.
The following attributes are associated with pinch ing ( l-'ig. 53):
Surface Markings. Usually none. The surface tends to be relatively smooth and regular, making finishing hy scraping, trimming, etc. unnecessary. Refinement by burnishing or polishing likely.
Surface Finish. Smooth unless altered by later operations.
Su rface Deposits and Segregation Effects.
Normally none.
Variations in Wall Thickness. Regular, rhythmic, shallow indentations moving upward vertically, each line directly above the other. The size and shape of the indentations correspond to fingertips.
Fracture. No special characteristics.
Preferred Orientation of Inclusions. May be ver tical in a cross section cut perpendicular It) vessel stance, but orientation is not strong. In X-radiographs, all inclusions are parallel to the surface, but no hori zontal or vertical orientation is obvious. Appearance is essentially the same as obtained using beater and an vil, but without evidence of compaction.
Particle Size Distribution. No distinctive rela tionships; a wider range can be tolerated than with most other techniques.
Vessel Shape. If used as a primary forming tech nique. round bases and small vessels are characteris tic. If used as a secondary technique, any shape can be produced.
Fig. 53. Attributes associated with pinching, a, Rhythmic, closely spaced grooves, especially on the interior surface, b, Preferred orientation of inclusions in cross section, c, Random orientation of inclusions in a radiograph taken normal to the surface (black voids, white = mineral grains), d-e, Typical vessel shapes; maximum diameter 20 cm.
b
Slab Building
Flat slabs are formed hy pressing the clay on a Hat surface, by rolling it on a flat surface with a cylindrical tool or by flattening it between the hands. The edges are joined by pressing or smearing (Fig. 54). This tech nique is well suited for rectangular shapes and for pro ducing large vessels rapidly. It is difficult to recognize from archeological specimens, blit should he consid ered a possibility whenever very large vessels are en countered.
The following attributes are associated with slab building ( Fig. 55):
Fig. 55. Attributes associated with slab building, a. Typical box shape, with sharp corners where slabs join, note rounding of corners on the interior, b, Surface markings, either uniform texture or combing at different angles, c, Preferred orientation of inclusions parallel to the surface seen in cross section, d, Random preferred orientation in radiograph taken normal to the surface, e, Large size of vessels: dotted lines show the typical arrangement of slabs in a series of tiers.
72 POTTERY TECHNOLOGY