Study of forming techniques

The different modes of forming a vessel leave distinct signatures in the ware. When the potter is making a vessel, shaping and squeezing the clay, a great number of pores are also formed. The way the pores are oriented in the ware tells us if the potter was using e.g. coiling technique, pulling technique, etc. The forming mode may be more or less easy to distinguish in the breakage of a sherd and in some rare cases, it is possible to determine the technique through observing a fresh breakage. The polished breakage or a thin section of the sherd gives a better image of the pore structure. However, even here it is often difficult to accurately decide the forming technique.

In this study the polished breakage of the sherd – orientation 90 degrees to the rim plane – is impregnated with araldite plastic mixed with a fluorescence agent and then polished again. The sherd is thereafter studied under a stereo microscope with the aid of a UV-light. Now even the orientation of very thin pores may be observed.

To test the applicability of the method simulated manufacture of four different vessels with known forming techniques were made. Among these there are two types of coiling technique, the U- and the N-technique, and two types of modelling technique. One method is simply to shape a vessel by pressing the vessel walls out of a lump of clay with the fingers. The other technique starts by pulling a thick coil of clay, using the fingers of one hand on the inside of the vessel and the other hand as support on the outside. The pore structure of these simulated manufactured vessels was then studied using the method described above. As seen in the illustration, there is a clear difference in the mode of the pores when a coiling technique or a modelling technique is applied. The difference between the U- and the N-techniques is also evident. In both cases the pores are oriented from one wall surface to the other. The U-technique gives a distinct curving of the pores whereas the pores produced by the N-technique have a diagonal orientation. In both techniques the individual coils are also clearly visible.  To distinguish between the two modelling techniques on the other hand is not as clear. The orientation of the pore structure is in both cases parallel to the wall surfaces.

Forming

Figure with the different forming techniques: a. U-technique. b. N-technique c. Modelling out of a lump of clay with the fingers. d. Modelling by pulling a thick coil of clay.

The method has been successfully tested on archaeological material in four ongoing research projects (Lindahl & Pikirayi 2010; Lindahl & Winter forthcoming, project title “Mechanisms of change: Technological choice as a challenge to daily practice and the negotiation of identities”; Lindahl & Stilborg forthcoming, project title “Late Black Earthenware- The introduction of modern pottery in Sweden”; Winter, Clark & Lindahl forthcoming, project title ”Ceramics from the Mariana Islands; laboratory analyses” )

Anders Lindahl


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