Natural Science in Archaeology

8.4 Tempers 189
gray or reddish-brown sandy pottery, a finegrained, very hard dark gray ware, or a
unique fine-grained black pottery made into thin-walled vessels. During the Shang
and Zhou Dynasties, the Chinese developed high-fired stonewares, began using
kaolinite, and developed glazing. During the Zhou Dynasty, they made a high-fired
and glazed product with kaolinitic clay that produced a finish that resembled jade.
Lead glazes were introduced during the Han Dynasty; perhaps traders from the
Middle East brought the use of lead to China. However, the Chinese were the first
to make high-lead bronzes, so they may have introduced lead glazes independently
because they were familiar with lead minerals.
The color of ceramic vessels depends on two variables. One is the content of
iron, manganese, and organic matter in the raw clay. The other is the temperature
and the atmosphere (oxidizing or reducing) of the firing.
Mineralogical and chemical characterization of ancient pottery is now commonplace
(Blackman 1981; Noll 1981). Such studies can give direct evidence of temper
materials and indirect evidence of the clay paste used. Blackman (1981) presents a
quantitative picture of the influence of the temper on the chemical composition of a
hypothetical parent clay body.
Although the three major clay groups (kaolinite, illite, and montmorillonite)
have distinctly different chemical compositions, most ancient pottery was made
from a mixture of these clay groups as well as other minerals present in the clay
deposit exploited. Fred Matson (see Matson 1965) taught the author in the field in
southwestern Greece how wide a variety of local soil and sedimentary clays can be
made useful for household pottery. After analyzing a variety of ancient Egyptian
painted ceramics for 8 years, Noll (1981) notes, “the ceramic material itself . . . is
rather uniform.” Noll found that two clay sources were used in ancient (and modern)
Egyptian pottery. Lime-rich pottery utilized the marly clay of the Qena area
that contained quartz, feldspar, hematite, and diopside. Lime-poor pottery made of
Nile mud contained quartz, feldspars, mica, and hematite.
To understand the local raw material base for pottery making, one needs to know
the local surficial geology and pedology. If sedimentary rocks are also potential
sources, then knowing the bedrock geology is also essential. Although X-ray diffraction
and chemical analyses are useful in ceramic studies, thin-section analysis
utilizing a polarizing microscope is the best single method for determining the raw
materials, especially tempers, and the technology of ceramic production. Books
focusing on results of ceramic petrography include Freestone et al. (1982), Jones
(1986), and Middleton and Freestone (1991).
8.4 Tempers
To reduce shrinkage of the final product and/or improve workability of the raw
material, temper is added to the clayey material. By definition, temper is something
the potter added to the clay to modify its properties. A wide variety of raw
materials have been used as temper: quartz sand, shells, calcite, mica, crushed rock