Thin-Section Petrography of Ceramic Materials by Sarah E. Peterson Philip P. Betancourt

Author:Sarah E. Peterson, Philip P. Betancourt [Sarah E. Peterson, Philip P. Betancourt]
Language: eng
Format: epub
Tags: Social Science, Archaeology
ISBN: 9781623031268
Google: TcktEAAAQBAJ
Barnesnoble:
Goodreads: 18202560
Publisher: INSTAP Academic Press
Published: 2009-08-10T00:00:00+00:00

Figure 6. Photomicrograph of a thin section of a vessel from Kommos, Crete, displaying a microfossil inclusion within the fabric (after Myer and Betancourt 1990, pl. A, sample no. T 111). Width of field = 1.2 mm.

Figure 7. Photomicrograph of a thin section of a vessel from Kommos, Crete, displaying characteristic “soda straw” plagioclase crystals within a particle of basalt (after Myer and Betancourt 1990, pl. A, sample no. T 190). Width of field = 0.8 mm.

It is sometimes possible to differentiate between natural inclusions and added temper; the latter may be discernable based on abundance, composition, size, shape, and distribution throughout the ceramic fabric, depending on the potter’s treatment of the material prior to its addition to the paste. Non-plastic inclusions may be ground or crushed to obtain a necessary size or texture, mixed with other raw materials, or processed through decantation or separation (Shepard 1956, 117; Reedy 2008, 131, 151). The large phyllite inclusions visible in Figure 1, for example, are rounded, an indication that they were weathered prior to their inclusion in the ceramic paste. Therefore, the non-plastic inclusions present in this fabric were either a naturally occurring component of the clay source or were not processed prior to their addition to the fabric. By contrast, the large, angular qualities of the calcite and dolomite inclusions present in Figure 5 signify that these inclusions were likely crushed or ground prior to their intentional addition to the paste. Grog tempers will also commonly exhibit angular properties when observed in thin section, and many organic tempers burn out of the clay fabric during firing and can be identified by the appearance of carbonized (black) spots or by voids or vugs left behind (Whitbread 1986, 82; Orton, Tyers, and Vince 1993, 133–135; Velde and Druc 1999, 142–144; Reedy 2008, 184–189).

The minerals in a ceramic fabric can often provide general information about firing as changes in mineralogy can occur when certain temperatures are reached, although these alterations are more often detected with x-ray diffraction, infrared spectroscopy, and other methods rather than through thin-section analysis (Reedy 2008, 184–185). The understanding of firing conditions can be complicated, however, as other factors such as the rate of the rise in temperature or the atmospheric conditions during the process will also affect the properties of the fabric (Orton, Tyers, and Vince 1993, 133–135; Velde and Druc 1999, 96–104; Reedy 2008, 184).

The forming technique utilized in the production of a ceramic material can sometimes be ascertained through the analysis of non-plastic inclusions in thin section, as the method utilized during the forming of a clay paste into a desired shape will align non-plastic inclusions in characteristic ways. When pottery is wheel-thrown, for example, particles will be arranged parallel to the rim and base of the vessel. Other types of alignment observed in thin section will be indicative of other forming techniques, and the arrangement of inclusions is also dependant on the orientation of the section taken for analysis (Shepard 1956, 183–186; Woods 1985; Whitbread 1996; Roux and Courty 1998; Reedy 2008, 180–184).

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