COMMENTS ON M. S. TITE, V. KILIKOGLOU AND G. VEKINIS, ‘REVIEW ARTICLE: STRENGTH, TOUGHNESS AND...

8/13/2019 COMMENTS ON M. S. TITE, V. KILIKOGLOU AND G. VEKINIS, REVIEW ARTICLE: STRENGTH, TOUGHNESS AND THER

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Strength, toughness and thermal shock resistance of ceramics 163Archaeometry45, 1 (2003) 163183. Printed in Great Britain

University of Oxford, 2003

COMMENTS ON M. S. TITE, V. KILIKOGLOU AND G. VEKINIS,

REVIEW ARTICLE: STRENGTH, TOUGHNESS AND THERMAL

SHOCK RESISTANCE OF ANCIENT CERAMICS, AND THEIRINFLUENCE ON TECHNOLOGICAL CHOICE,

ARCHAEOMETRY, 43(3) (2001), 30124, AND REPLY

This series of comments on Tite et al. was initiated by J. K. Feathers. Subsequently, M. B.

Schiffer commented on both Tite et al. and Feathers, and B. Sillar commented on Tite et al., on

Feathers and on Schiffer.

COMMENTS I: ACCOUNTING FOR CERAMIC CHANGE

J. K. FEATHERS

University of Washington, Department of Anthropology, PO Box 353100, Seattle, Washington 98195-3100, USA

The recent review of strength, toughness and thermal shock resistance of ancient ceramics by

Tite et al. is a welcome addition to studies of ceramic change in the archaeological record. The

authors question the degree to which these properties may have influenced changes of temper

evident in the record. They contrast, on the one hand, those who have correlated changes in

temper with changes in these properties and assumed a causal relationship (e.g., Neupert 1994)

with, on the other hand, those who dismiss such correlations as incidental (e.g., Woods 1986).

Trying to maintain some middle ground, the authors call for an increased understanding of how

different tempers affect such properties, to provide a baseline for explanations of technological

change that may include many other factors.

While not disagreeing with this latter point, I wish to expand on how one might build an

argument showing whether or not these properties are determining factors. I phrase my com-

ments in the language of evolutionary theory, which I have found useful for understanding

ceramic changes (Feathers 1990, 2002; Dunnell and Feathers 1991: see also Neff 1992; Teltser

1993; OBrien et al. 1994; Pierce 1999; Pool and Britt 2000). I use as an exampleone cited

extensively by Tite et al.the increase to high frequency of shell temper that swept acrosseastern North America during the later prehistoric period. This was not a localized change, but

one that affected a large territory, spreading from Midwestern river valleys along the Gulf and

Atlantic seaboards, and on to the Great Plains. Only in the extreme south-east (peninsular

Florida, parts of Georgia and also parts of Louisiana) and the north (Great Lakes region,

northern New England and Canada) did shell-tempered pottery not appear, or did so only in

small quantities. While the timing of the change is not well dated, shell-tempered pottery did

occur, with one minor exception (Gleach 1988), late in prehistory and was the pottery in use at

the time of European contact.

The change to shell temper is a phenomenon that has puzzled archaeologists for at least a

century (e.g., Holmes 1903). Availability was not a problem, at least along the coasts, where


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164 J. K. Feathers

various marine shellfish are common, and in the interior Southeast and Midwest, where river

mussels were abundant. This raises the question of why shell was not utilized in any appreci-

able amount earlier, because the replacement by shell of earlier tempers, when it did happen,

was nearly complete, covering the entire range of pottery forms and uses. Other tempers, such

as sand and grog, were mixed with shell to varying degrees in different places, but these wereseldom predominant. A distinction has often been made between fine- and coarse-grained shell

temper, this often being assumed to represent functional differences between serving and more

display-oriented uses on the one hand and storage and cooking uses on the other, but the

relationship between temper size and other functional variables has been shown to be more

complex than a simple dichotomy (Teltser 1993). The change to shell tempering occurred in

some places at a time when there was little else that changed in the record, including settlement

and subsistence (e.g., Dunnell and Feathers 1991), although some correlation can be drawn

between shell-tempered pottery and maize agriculture.

While Tite et al. are certainly correct in calling for more systematic measurements of strength,

toughness and thermal shock resistance for various tempered pottery, the evidence that hasbeen collected so far (Steponaitis 1983, 1984; Feathers 1989, 1990; Feathers and Scott 1989;

West 1992) suggests that shell temper increased both pottery toughness and thermal shock

resistance over earlier temper types. Making that assumption, the question remains whether

the temper change can be accounted for by this improvement in mechanical and thermal

properties.

The first concern is whether the change is even functional, in the sense of affecting the fitness

of the ceramic and therefore the probability of selection (Dunnell 1978), and not stylistic. Style

in the evolutionary literature refers to neutral traits, or those with equivalent selective value,

whose distribution is affected entirely by transmission mechanisms. This is a concept with a

long intuitive history in American archaeology (e.g., Kidder 1915; Ford 1938; Krieger 1944)and developed formally by Dunnell (1970, 1978, 1980, 1986). Some have questioned whether

any trait is completely stylistic in this sense (e.g., Shennan and Wilkinson 2001), but studies of

the distributions of some, mainly decorative, traits have shown some resemblance to the stochastic

distributions that neutral traits ought to follow, and thus these traits can effectively be con-

sidered style (Neiman 1995; Lipo 2001). The rise in frequency of shell tempering, on the other

hand, has a distinctively different distribution in most parts of eastern North America: a long

period of low frequencies, a sudden increase to high frequencies and then maintenance of the

high frequencies. Figure 1 shows this distribution from different parts of the Lower Mississippi

Valley. This certainly appears to be a functional rather than stylistic change, as these terms are

defined in evolutionary archaeology.Unlike many definitions of style, style as neutrality has empirical implications that can be

tested. Tite et al. define style more in terms of the technological styleof Lechtman (1977), or

a way of doing things that culturally structures the kinds of changes that can occur. Rindos

(1985) referred to something similar as cultural selection of the second kindas opposed to

cultural selection of the first kind, which is an analogue to biological natural selection. Such

a distinction may not be necessary. Evolutionary theory in biology has long recognized that

selection is conditioned by historical and architectural constraints (Gould and Lewontin 1979).

Such cultural constraints might be what archaeologists commonly think of as tradition (Neff

1992).

But even if the change to shell tempering was functional, was it the properties of the temperitself that caused this rise? And if it was the properties, was it strength, toughness or thermal

shock resistance? In other words, was the increase in these properties merely incidental to


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Strength, toughness and thermal shock resistance of ceramics 165

Figure 1 Frequencies of shell-tempered pottery for assemblages from different portions of the Lower Mississippi

Valley (shown as lines connecting data points). The data are drawn from surveys by Phillips, Ford and Griffin

(1951) and by Ford (1952), from various references listed in OBrien and Wood (1998) and from Feathers (1990).

The assemblages from these surveys cover a large portion of the valley, are reasonably placed in time by seriations,

and are quantified by ceramic type. Additional discussion of this data can be found in Feathers (2001), a copy of

which can be obtained electronically from the author. Note that the rise in frequency of shell tempering occurred

earliest in the northern part of the valley (SE Missouri, Malden Plain, Memphis, St Francis), later in the central

part (Upper and Lower Yazoo, Lower Arkansas) and not at all in portions of southern Louisiana (Lower Red

River).

changes that were occurring for other reasons, the point made by Woods (1986)? Several

possibilities can be imagined for how high frequencies of shell-tempered pottery could have

been selected, without mechanical and thermal properties being the causal factors:

(1) Shell-tempered pottery was not selected for, but rose in frequency because of higher-level

processes. Evolutionary theory in archaeology has long recognized that selection can happen

on different levels (Neff 1992). Changes at higher levels can affect traits at lower levels. For

example, shell-tempered pottery is no longer made in eastern North America. This is not

because of anything to do with the properties of the pottery, but because the people who made

the pottery were largely driven into extinction by the introduction of European contagious

diseases. (Other, lower-level processes may have been involved as well. Any surviving pottersfaced completely new selective pressures brought about by cultural reorganization and expos-

ure to European goods.) Similarly, as mentioned before, a high correlation between shell-

tempered pottery and maize agriculture has often been noticed (Osborn 1988; Feathers 2001).

Perhaps pressure for available farming land forced maize farmers to expand at the expense of

their neighbours. In this case there may have been no selection forshell-tempered pottery, but

shell-tempered pottery was selected because of the selection of maize-growing groups who just

happened to make such pottery. Such migration is a traditional explanation in American archae-

ology for the rise of shell tempering and one that could well be true in some places, but lacks

much empirical evidence as a regional explanation. The shell-tempered pottery that rose in

frequency often resembles more the local pottery it replaced than any possible external source(Feathers 2002). [The distinction between selection for and selection of is often made in

evolutionary theory (e.g., Sober 1984). How can one show selection forshell tempering? One


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166 J. K. Feathers

clue may be other changes in the ceramics. Early shell tempering in southeastern Missouri,

for example, was accompanied by an increase in porosity (Feathers 2002). The early shell-

tempered pottery was also heavily slipped. This has not been thoroughly investigated, but it is

possible that the slips counteracted the high porosity. If so, the high cost of slips would not

have been tolerated had not the advantages of shell tempering far outweighed the disadvan-tages. Porosity in later shell-tempered pottery is reduced and, interestingly enough, slips drop in

frequency to low levels.]

(2) Shell tempering was selected for, but for reasons unrelated to pottery use. This might

encompass some of the socio-politico-ideological factors to which Tite et al. refer. Evolution-

ists in archaeology have referred to non-subsistence-related attributes as waste, a term that

should not be confused with its common English connotation of worthlessness. Explanations

for the selection of waste have included bet-hedging under conditions of environmental uncer-

tainty (Dunnell 1989; Madsen et al. 1999) or costly advertising under conditions of economic

competition (Neiman 1997). By contrast, the Late Woodland period in eastern North America,

when shell tempering rose in frequency, is generally regarded as a time of economic andpopulation expansion because of the increased productivity of maize agriculture (Steponaitis

1986; Bense 1994). This was not a time of economic stress, and in fact not much waste is

evident, unlike the Middle Woodland period that preceded it or the Mississippian period that

followed it. In many locales pottery as well as other artefacts had few decorative features, and

other evidence for wasteful behaviour, such as building mounds, is absent. Utilitarian con-

cerns seem to have driven most activity during this time.

(3) Shell tempering was selected for because of ceramic properties it imparted, but not because

of mechanical or thermal properties. For example, Osborn (1988), noting the correlation with

maize, suggests that the carbonate in the shell provided lime that increased the nutritional value

of maize. While this is perhaps true, he does not demonstrate that shell temper provides thelime slaking necessary for the desired effects or, even if it does, that this played a role in the

rise of shell tempering. His hypothesis remains speculation, because he did not provide any

empirical implications that can be tested. As another possibility, I have demonstrated that

shell tempering increases the workability of the raw clay (at least of that collected from south-

eastern Missouri). But I have found no evidence that this played a causal role either (Feathers

2002). An advantage of increased workability would be wider morphological possibilities.

However, at least in southeastern Missouri, the early shell-tempered pottery does not differ

greatly in morphology from the sand-tempered pottery that it replaced (Feathers 2002). More

varied morphology does occur later on, suggesting that improved workability, once present,

was eventually taken advantage ofa process called exaptationin evolution (Gould and Vrba1982).

How does one actually show that mechanical and thermal properties were causal in the selec-

tion of shell tempering? I have concluded this for southeastern Missouri only by a process of

eliminating other possibilities. If other factors can be ruled out, then stronger pottery will be

selected if for no other reason than lower replacement costs. Granted I may have not thought of

all possibilities, but for now the hypothesis that mechanical and thermal properties were the

causal factors has not been disproved. Tite et al.s (2001) criticism of Neupert (1994) needs to

be considered in this light. Neupert maintains that the reason for a change from sand to grog

temper among Cibola white wares in the southwestern United States was increased strength.The criticism that Neupert has not considered other possibilities is fair but, again, if such

possibilities can be ruled out, the strength hypothesis cannot be disproved.


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I rush to add that the explanation of shell tempering that I have constructed for southeastern

Missouri cannot be extrapolated to the rest of eastern North America. Because of the historical

contingency of evolution, one cannot generalize from place to place. The rise in frequency of

shell tempering may have been for different reasons elsewhere. But what could explain the rise

in frequency in so many different places across the East at roughly the same time? I am notconvinced that thermal and mechanical properties are the full answer. Strength and related

properties can be increased in a lot of different ways, as Tite et al. point out. Why shell? Why

during the Late Woodland?

I have suggestedand it is no more than a suggestion at this pointthat the unusual firing

requirements of calcium carbonate based temper may provide an answer (Feathers 2002). To

prevent lime spalling, firing temperatures cannot exceed a certain threshold. [While other

means to prevent lime spalling, such as the addition of salt, are possible, little evidence has

been presented that these practices were employed in prehistoric North America. Possible

evidence of salt addition in the Upper Mississippi Valley (Stimmel et al. 1982) has not been

found elsewhere (OBrien et al. 1994).] Prior to the rise of frequency of shell tempering, firingwas perhaps not so controlled that using shell entailed a large, intolerable risk of vessel failure.

Change in firing practices during the Late Woodland may have reduced this risk and allowed

shell-tempered pottery to be produced in large numbers where it was only a minor variant

before. Then, whatever advantages shell-tempered pottery had from place to placegreater

strength in southeastern Missouriallowed the sharp increase. The analysis of colour, firing

temperatures and firing atmospheres has demonstrated an increase in reduction, which will

delay carbonate decomposition, in southeastern Missouri just prior to the rise in frequency of

shell-tempered pottery (Feathers et al. 1998). This change in firing practices may have occurred

because of change in fuel. Widespread clearing due to the spread of maize agriculture altered

the kinds of fuel used in the St Louis area at this time (Johannessen 1984; Rindos and Johannessen1991). This is a hypothesis that does have empirical implications that can be tested (Feathers

2002). Did firing practices and fuel use change in other parts of the East at this time, when

clearing for agriculture must also have been occurring? If not, other reasons must account for

the rise in frequency of shell-tempered pottery in these areas.

I have taken pains to show that whether or not changes in temper can be attributed to changes

in mechanical and thermal properties of the pottery is strictly an empirical matter. Few gener-

alizations about shell temper or any temper apply everywhere at every time. In this regard,

Woods (1986) observations about the relationship between temper and these properties in

Britain are largely irrelevant to the North American case. She argues that selection of temper

in Britain reflected geological availability more than concern with mechanical or thermal prop-erties. All this means is that the selective pressures governing availability were stronger than

those governing performance in Britain. As long as minimum performance requirements are

met, pottery is free to vary according to other selective pressures and random processes. Where

these pressures are relatively weak, performance requirements will carry a stronger causal role.

Ethnographic evidence (e.g., Miller 1985) that pottery does not correspond to functional per-

formance criteria is only recognition of such variable selective pressures. Pottery is often a

compromise to meet competing pressures and, again, sorting out the different possibilities is an

empirical matter. Woods (1986) ends her argument with a call for a more emic approach, but

motivations of prehistoric potters are not possible to verify. What is needed is to structure a

series of hypotheses so that empirical implications can be drawn and tested, such as I have triedto demonstrate for North American shell tempering. Otherwise, we abandon science in favour

of speculation.


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168 J. K. Feathers

ACKNOWLEDGEMENTS

This contribution benefited from comments by Robert Dunnell.

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COMMENTS II: PROPERTIES, PERFORMANCE

CHARACTERISTICS AND BEHAVIOURAL THEORY

IN THE STUDY OF TECHNOLOGY

M. B. SCHIFFER

Department of Anthropology, University of Arizona, Tucson Arizona 85721, USA

Papers that advance our understanding of ceramic technology, such as those by Tite et al. and

Feathers, are increasingly welcome in an archaeology attuned to the importance of archaeometric


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170 J. K. Feathers

research. I have a few comments to add, mostly by way of clarifying important concepts,

particularly propertiesand performance characteristics. I also discuss the relevance of beha-

vioural theory for explaining technological change.

Before the term technological choice becomes fully entrenched in archaeology, I sug-

gest that we become aware of its appreciable ambiguities. In their use of the term, Tite et al.denote a clay artisans choice among available alternatives, such as type of temper or sur-

face treatment. Schiffer and Skibo (1987, 1997) have previously called attention to this kind

of choice as the central explanatory problem when we address variability in artefact design; we

labelled it technical choice. In contrast to the narrow and well-established meaning in archae-

ology of technical choice, technological choice is a term with many meanings. For example,

some writers use technological choiceto designate choices made by the consumers or adopters

of products such as finished pots (for examples, see Lemonnier 1993). Thus, people select at a

market among the products of different artisans. Because of its polyvalency, I believe that the

term technological choice should be avoided, at least when the intended meaning is the

behaviour of the artisan.In these papersand a great many othersthere is a tendency to conflate the concepts of

material property and performance characteristic. A scientific explanation of artefact design

requires that we keep these distinct. Let me now present a simple framework that can help

to illustrate the difference (see Schiffer and Skibo 1997; Kingery 2001; Skibo and Schiffer

2001). The technical choices executed by an artisan impart to an object certain properties,

which in principle could be measuredqualitatively or quantitativelyin a laboratory setting.

Indeed, these properties pertain to the materials from which the object was made, and so

could in many instances be measured on samples of the material itself; and some can only

be assessed in this manner. Tite et al. discuss relationships among several strength and

thermal properties of ceramics. These discussions concern material properties, a product oftechnical choices, which can be defined and measured without reference to post-manufacture

activities.

In addition to directly affecting material properties, technical choices also determine such

measurable attributes of an artefact as shape, size, weight and so forth. Formal property is

usually the term that archaeologists apply to such measurable quantities and qualities of objects

(although sometimes both material and formal properties are lumped together as formal properties

e.g., Rathje and Schiffer 1982, ch. 4; Schiffer 1996a, ch. 2). Material properties can influence

formal properties, as is obvious for weight, but measuring a formal property generally requires

operations on objects. Needless to say, measurements of formal properties can often be conducted

outside the laboratory, as in ethnoarchaeological settings. Like material properties, the formalproperties imparted by the artisan can be measured without reference to post-manufacture

activities.

Clearly, an appreciation for material properties and formal properties helps us to frame

questions about the effects of technical choices on the materiality of finished products. But it

does not enable us to answer all our questions about technical choices, artefact design and other

technological processes. To take that next step requires that we consider the interactions among

the artefact of interest with people and other artefacts, particularly in post-manufacture activit-

ies. The concept of performance characteristic enables us to make assessments of an artefacts

suitability for taking part, appropriately, in given interactions. A performance characteristic,

then, is an interaction and/or activity-specific behaviouralcapability (see Schiffer and Miller1999, ch. 2). Performance characteristics, which presume the materiality of an object as manifest

in material properties and formal properties, must be defined in relation to given interactions

170 M. B. Schiffer


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in real-world, not laboratory, activities. In short, performance characteristics are underdeter-

mined by material properties and formal properties.

Heating effectivenessis an example of a performance characteristic that can highlight the

difference between performance characteristics, on the one hand, and material properties and

formal properties, on the other. Heating effectiveness has been defined as the rate at which avessel heats its contents (Schiffer 1990, 374), a performance characteristic believed to be

relevant to determinations of a vessels fuel efficiency. As such, heating effectiveness can only

be measured in a real-world settingthat is, people cooking with the potor in a laboratory

experiment that mimics relevant interactors and interactions. I chose the latter strategy in

experiments that sought to ascertain the effects of traditional surface treatments on heating

effectiveness.

In the laboratory, I measured the time required to heat water to 90oC in miniature vessels

held over a tiny Bunsen burner. In making the pots, all technical choices (except surface

treatment) were held constant. Thus, only material properties and formal properties relating to

surface treatments varied among the vessels. The results furnished a relativemeasure of theheating effectiveness of varying interior and exterior surface treatments. It was found that

values of heating effectiveness were strongly affected by two material properties: the

permeabilities of the interior and exterior surfaces. By changing the experimental conditions

(technical choices of pottery manufacture, nature of the heat source, kind of contents, juxta-

position of pot and heat source), one could have discerned effects on heating effectiveness of

other material properties (e.g., thermal diffusivity) and formal properties (e.g., vessel thickness

and shape). However, knowledge of all material and formal properties alone could never allow

determination of heating effectiveness values; one must also know something about the interactors

and interactions of actual pot use.

Sometimes it seems that a performance characteristic is uniquely determined by one materialor formal property. For example, the liquid-holding capacity of a vessel would appear to be

equivalent to its total volume. However, if that vessel is used to transport water on a daily basis,

the liquid-holding capacity, as a behaviourally relevant performance characteristic in that activ-

ity, would always be less than the vessels total capacity. In every such case, a consideration of

other interactors and interactions in post-manufacture activities can lead to the specification of

performance characteristics.

The need to distinguish among material properties, formal properties and performance char-

acteristics only became clear to us after many years of effort to understand technological

variability. Indeed, when trying to employ our findings in explanations of artefact design and

adoption processes, we came to appreciate that the explanatorily relevant factors were perform-ance characteristics (e.g., Schiffer 1995; Schiffer and Skibo 1997). We hope that this clarifica-

tion will enable other investigators to more finely hone their questions about technological

change.

Feathers proposes that an appropriate framework for explaining technological change is

Darwinian evolutionary theory, as construed by Robert C. Dunnell and his followers. Invest-

igators who maintain this perspective are known as selectionists, because they usually invoke

some kind of natural selection to explain the differential persistence of discrete variants of

traitsattributes or artefact types. [In a previous paper, I assessed in some detail the strengths

and weaknesses of the selectionist programme from the perspective of a behavioural archaeo-

logist; see Schiffer (1996b).] Selectionists have appreciated the profound difficulties of demon-strating how specific trait variants affected the biological fitness of the human populations

that adopted them (in relation to other variants). That is why many selectionists today, such as


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172 J. K. Feathers

Feathers, advocate a more modest agenda: studying the replicative success of specific traits.

When framed in this way, the programme still appears evolutionary, but it is an evolution of

artefacts, not of human populations. If we want to conceive of technological change in terms

of competitions among artefact types, then we already have in archaeology a programme

that has been very successful in addressing such research questions. It is known as beha-vioural archaeology (for a general introduction to the programme, see LaMotta and Schiffer

2001).

In this limited space I cannot begin to lay out the many principles and strategies of behavi-

oural approaches to technology. However, I do want to emphasize that behaviouralists, who in

all of their studies focus initially on the concrete interactions among people and artefacts,

recognize the need for developing many kinds of theory for tackling questions of technological

change. For example, we have developed theories (and methods) for explaining artefact design

(e.g., Schiffer and Skibo 1997; Skibo and Schiffer 2001), adoption patterns (e.g., Schiffer

1995), and even large-scale processes such as competitions among aggregate technologies

(Schiffer 2001) and technological differentiation (Schiffer 2002). Not surprisingly, in manybehavioural theories performance characteristics are important variables. A recent paper by

Schiffer et al. (2001) is a reference-rich summary of behavioural approaches to studying tech-

nology. In behavioural archaeology, I believe, one can find an array of conceptual tools that

enables investigators to bridge the sometimes considerable gaps between archaeometric ana-

lyses and considerations of human behaviour in its varied contextssocial, political, religious

and so on.

REFERENCES

Kingery, W. D. 2001, The design process as a critical component of the anthropology of technology, inAnthropological

perspectives on technology(ed. M. B. Schiffer), 12338, University of New Mexico Press, Albuquerque.

LaMotta, V. M., and Schiffer, M. B., 2001, Behavioral archaeology: towards a new synthesis, inArchaeological theory

today(ed. I. Hodder), 1464, Polity Press, Cambridge.

Lemonnier, P. (ed.), 1993, Technological choices: transformation in material cultures since the Neolithic, Routledge,

London.

Rathje, W. L., and Schiffer, M. B., 1982, Archaeology. Harcourt Brace Jovanovich, New York.

Schiffer, M. B., 1990, The influence of surface treatment on heating effectiveness of ceramic vessels, Journal of

Archaeological Science, 17, 37381.

Schiffer, M. B., 1995, Social theory and history in behavioral archaeology, inExpanding archaeology(eds. J. M. Skibo,

W. H. Walker and A. E. Nielsen), 2235, University of Utah Press, Salt Lake City.

Schiffer, M. B., 1996a, Formation processes of the archaeological record, University of Utah Press, Salt Lake City.Schiffer, M. B., 1996b, Some relationships between behavioral and evolutionary archaeologies, American Antiquity,

61, 64362.

Schiffer, M. B., 2001, The explanation of long-term technological change, in Anthropological perspectives on techno-

logy(ed. M. B. Schiffer), 21535, University of New Mexico Press, Albuquerque.

Schiffer, M. B., 2002, Studying technological differentiation: the case of 18th-century electrical technology, Amer-

ican Anthropologist, 104, 114861.

Schiffer, M. B., and Miller, A. R., 1999, The material life of human beings, Routledge, London.

Schiffer, M. B., and Skibo, J. M., 1987, Theory and experiment in the study of technological change, Current

Anthropology, 28, 595622.

Schiffer, M. B., and Skibo, J. M., 1997, The explanation of artifact variability, American Antiquity, 62, 2750.

Schiffer, M. B., Skibo, J. M., Griffitts, J. L., Hollenback, K. L., and Longacre, W. A., 2001, Behavioral archaeology

and the study of technology,American Antiquity

, 66, 72938.

Skibo, J. M. and Schiffer, M. B., 2001, Understanding artifact variability and change: a behavioral framework, in

Anthropological perspectives on technology (ed. M. B. Schiffer), 13949, University of New Mexico Press,

Albuquerque.

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COMMENTS III: TECHNOLOGICAL CHOICES AND

EXPERIMENTAL ARCHAEOLOGY

B. SILLARInstitute of Archaeology, University College London, 3134 Gordon Square, London WC1H 0PY, UK

The paper by Tite et al. was a constructive review of progress in the study of the strength,

toughness and thermal shock resistance of ancient ceramics. In responding to Tite et al., and to

the commentaries by Feathers and Schiffer, I wish to highlight a few concerns that may be

relevant to future investigations of these material properties. I am particularly concerned to

draw attention to the context of vessel use and suggest that this may mean that alternative or

supplementary experiments should be considered. I also wish to highlight an issue that under-

lies all the papers: How can we use experimental archaeology to bridge the gap between thescientific (etic) study of universalmaterial properties and the local (emic) rationale underlying

the production and use of material culture?

TERMINOLOGY

I agree wholeheartedly with one aspect of the clarification in terminology suggested by Michael

Schiffer. It will be of use if we can distinguish between the material propertiesof the ceramic

fabric, the formal propertiesof the complete vessel and how these affected the vessels per-

formance characteristicswith respect to a specific activity. Within archaeology, this is largely

a distinction between the potentially measurable material properties of the fabric and the com-plete vessel and our assessment of their relevance during a hypothetical activity. The perform-

ance characteristicsof a cooking pot, for instance, will depend on the intensity and constancy

of the heat source, as well as the conductivity of the vessel and its contents. A pot used to toast

dry maize kernels by being balanced on three stones over a roaring wood fire will experience

different stresses to the same pot containing chicken stew and placed within a fan-assisted

electric oven. Any discussion of performance characteristics should therefore require some

comment about the specific activities being discussed, yet very few experimental studies have

given careful consideration to specific cooking methods, or other activities, within which the

vessels were expected to perform(see below).

Schiffer also makes a distinction between his term technical choice, as a subset of what herefers to as Lemonniers more encompassing term technological choice. Here we have two

major schools of thought trying to identify and define differences within their shared interest in

the social significance of technology. The two schools of thought are: American Behavioural

Archaeology, most cogently expressed in the work of Michael Schiffer; and French Sociology

and Ethnology of Technology, originating in the work of Mauss and Leroi Gourhan, but

developed and disseminated in the writings of Lemonnier and others. Schiffer is claiming both

primacy and greater utility for a more restricted meaning for the term technical choice:

[I]ndividual activities in material procurement and manufacture processes are known as tech-

nical choices (Schiffer and Skibo 1987, 599)(Schiffer and Skibo 1997, 29). When Lemonnier

writes in English he normally uses the term technological choice, but he also uses the termtechnical choice synonymously; for example, the notion of technical choice becomes the

focus of our research into the relationship between a society and the technical system it has


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174 J. K. Feathers

developed (Lemonnier 1993, 8). It is confusing to find that different people are applying

slightly different significance to the same terms, but I would like to add a word or two of

caution to Schiffers proposed clarification.

Schiffer identifies a clear distinction between the actions of a producer as opposed to more

general technical activities, including those of a consumer. To start with this distinction appearsa useful corollary to his separation of the mechanical properties imposed during production

and the performance characteristicsthat affect the vessels utility for a specific activity. How-

ever, our ability to separate out acts of production from acts of consumption depends on our

analytical focus. Consumption could be characterized as the use of the product of one technical

operation as a tool, or component, in the making of another, different, product or during a sub-

sequent activity. A pick is used to excavate clay, the clay is used to make a pot, the pot is fired

using wheat stalks and chaff as the fuel, the pot is used as a container in which to dye wool, the

wool is used to weave a sack, and the sack is used to transport ash as a fertiliser for the wheat

fields. Whether a technical act is seen as one of production or as one of consumption depends

on the particular focus of our analysisceramic specialists, textile analysts and archaeobotanistswould each define different steps in this process as production or consumption. Using the dis-

tinction suggested by Schiffer, I would have to separate my discussion of the potters technical

choice to burnish a pot from my consideration of the consumers technological choice to use a

stone as a burnishing tool, even though I am discussing the same technical act. At times we may

wish to clarify whether our analytical focus relates to the behaviour of the artisan when making

an object or the behaviour of the consumer when using it, but I do not think that Schiffers dis-

tinction between technical choiceand technological choiceis the clearest way to express this.

Another issue is the need to distinguish between the material consequences of the artisan s

actions and our interpretation of the reasoning behind these actions. Both technical choiceand

technological choice address the question of choice, and suggest a willingness to try andappreciate the agency behind peoples actions, not simply the physical properties of the artefact

(cf. Dobres 2000). Modern investigators are able to recognize these technological choices,

because our comparative approach makes us aware of alternative materials and methods that

achieve the same end (Schiffer and Skibo 1997, 29; Sillar and Tite 2000, 911). However,

unless we can demonstrate one technique being substituted for another during a period of

technological change, it is very difficult to use archaeological evidence to demonstrate that the

artisans themselves were aware of alternative techniques. Nonetheless, even if an artisan is not

aware of alternative choices, or there are no apparent functional reasons for selecting one

technique as opposed to another, this does not mean that the selection was arbitrary (cf.,

Latour 1993; Lemonnier 1993). The use of each technique during the production of an artefactis dependent on a wide range of related technical activities and it is also affected by the

historical, environmental, social, economic and ideological context of the artisan (Sillar and

Tite 2000). Any analysis of the cultural context of technological choicesmoves well beyond

the measurable properties of a specific technology, but it is a necessary step in our attempt to

understand the social context of the artisans, and this includes a consideration of the perception

and purpose behind their actions. In this context, I am happy to accept the wider significance

that Schiffer attributes to the term technological choice.

POTS AS TOOLS

Problemsexperienced during any technical activity may be addressed through adapting the

way in which a tool is used, as well as changing the material properties of the tool itself. With

174 B. Sillar


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specific reference to the use of a cooking pot, this may include the way in which the pot and its

contents are prepared, the cooking techniques selected, and the choice of fuels and heating

methods. Many of the technological choices that affect cooking pot performance are in relation

to the cooks techniques for selecting the cooking pot, preparing the hearth, positioning the pot

and tending the fire. Cooks use diverse strategies to reduce the risks of acquiring and using apot, the most common of which is to strike the rim with the finger to hear it ringa fairly

accurate test of whether a vessel has been suitably fired or has any major cracks. Consumers

also draw upon their cultural knowledge of appropriate or effective pots when deciding what to

acquire (Sillar 1997). When washing the pot, the cook frequently takes the opportunity to check

the vessel, particularly the base, and, if it shows signs of cracking, another vessel may be

selected rather than risk losing the contents during use (Sillar 2000, 138). The choice of pot will

also relate to the intended contents and the cooking method; one pot may be preferred for

leaving on the stove to simmer for several hours (a major technique in the Andes, where dung

can be used as a slow-burning fuel and water boils at lower temperatures due to the high

altitude) and a different vessel may be chosen when subjecting the contents to intensive speedheating using fast-burning fuels. The temperature gradient endured by a cooking pot will be

affected by these culinary technologies and may need to be considered when designing our

experiments. Repeatedly transferring briquettes from boiling water into icy water, or taking

them from the dry heat of a furnace and quenching them in cold water, may cause them to

suffer rapid temperature change, but how comparable is this to the temperature gradient experi-

enced by the fabric of a cooking pot where the outside of the vessel is at about 300500C and

the inside contents are at about 510C?

One consequence of these high temper concentrations and low firing temperatures is the

associated high porosity and permeability of the vessel wall, and hence the reduced heating

effectiveness of the resulting cooking pot (Tite et al., p. 322). I suspect that this statementsubsumes two or more factors that are at work. If a vessel is so porous that the water inside it

flows freely to the exterior surface, then the continual boiling and evaporation of this sur-

face water will effectively remove energy from the vessel contents and prevent heat transfer

through the vessel. Thus, when heating water in a highly porous organic tempered bowl, it

came within 12C of boiling but did not boil (Schiffer and Skibo 1987, 605). Equally, as

heat does not conduct well through air, the voids inside a dry porous fabric would also reduce

the conductivity of a cooking pot. However, when residues from previous activities allow the

liquid held in the vessel to saturate the pores but, at the same time, do not permit the water to

pass too rapidly through the fabric to the exterior surface, then, far from reducing heating

effectiveness, these saturated pores may actually increase heat conductivity and help to reducethe temperature gradient through the vessel wall during use. At the same time, the liquid- and

organic-impregnated pores of pottery fabrics would, like voids, help to arrest cracks prior to a

fatal fracture. Many of the cooking pots that I have used in the Andes are minimally porous

(i.e., if you fill them with water and place them on the floor for an hour, the floor underneath

gets slightly damp); however, this does not seem to prevent the cooksgetting a roaring boil

going. I suspect that as long as the water getting through the fabric is minimal, then the loss

of energy caused by water evaporating off the surface is not so great as to prevent sufficient

heat transfer through the fabric. In fact, it is essential to the function of a cooking pot that it is

not too efficient in heat transfer: pottery also functions as an insulator (preventing the pots

contents closest to the heat source from catching fire). Some Andean cooks will seasona newcooking pot prior to using it for the first time; for instance, by rubbing the inside and outside

with animal fat or blood, or boiling the dark water in which freeze-dried potatoes have soaked


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176 J. K. Feathers

and pouring this in (Sillar 2000, 138). These processes help to reduce the earthy flavour that a

new pot can impart to the food, and they also penetrate and help to seal up the pores of the

vessel. During use, the abundant micropores within the low-fired fabrics of a cooking pot

rapidly absorb organic materials from the food contents on the inside and the carbon and

hydrocarbons given off by the poorly combusted fuels on the outside. To what extent do thesecommon aspects of a cooking pots function change the properties of the fabric? This should be

considered when deciding to subject test pieces to dry heat followed by quenching, or when

attempting to replicate the actual use of the vessel. (One possibility may be to impregnate the

fabric with oils during the testing.)

The choice of pottery forming technique will also affect the performance characteristics of

the fabric. The forming technique can affect the bonding within the clay and between the clay

and the inclusions, as well as the alignment of the clay crystals and inclusions within the fabric.

Platy inclusions, such as mica, shell or talc, only have a beneficial effect on strength and impact

resistance when the platelets are aligned at 90to the direction of impact or stress (cf., Feathers

1989). If these platelets were in the same direction as the impact then, like slate, they wouldprovide a fault line for cleavage to pass through. One of the reasons why I think most potters

take such care over finishing the rim of each pot is because it requires different finishing tech-

niques to facilitate the changing direction of the inclusions, as well as the stresses and strains of

differential drying, all of which make the rim particularly susceptible to the propagation of

cracks. Rye (1981) has demonstrated how the direction of inclusions is affected by the choice

of forming technique, and we should be considering this as a further aspect of our analysis of

how the production techniques affect the performance characteristics.

I suspect that lime spalling is primarily a problemexperienced by collectors and museum

curators who want to treat the pots as ornamentalobjects: it may well be that pots that are

in frequent use are less susceptible to catastrophiclime spalling during their relatively shortuse-life. In Raqchi, Department of Cuzco, Peru, lime spalling has only became a signi ficant

problem since the potters started to make pottery for tourists. Prior to that, their pots were made

for domestic use, including the brewing of maize beer, and the potters did not notice any lime

spalling. I suspect that when the pots are subjected to a repeated throughput of water, the

re-hydrated lime is continually washed out of the vessel and lime spalling seems to become a

very minor problem (it is possible that a similar process takes place when potters quench calcite-

tempered pottery immediately after firing; cf., Carlton 2002). These suggestions are entirely

based on ethnographic observation and would benefit from experimental testing. The degree to

which these processes will prevent lime spalling should depend on the particular form and

quantity of the calcite, the temperature of the original firing, the porosity of the fabric, thechemical effects of the vessel contents and the regularity of use/washing, all of which will

affect the solubility of the lime. If my observations are correct, this would provide further

support for Osborns (1988) suggestion that the presence of lime may have added to the

chemical processing of maize in cooking pots.

Tite et al. (p. 322) call for a database of information on clays, tempers and firing temper-

atures used in the production of cooking pots. Ideally, this should be supplemented by archaeo-

logical and ethnographic data relating to how these vessels were used within each cultural

context. We should make careful observation of the overall form of each vessel in order to

asses where use-wear has occurred and what processes may have caused it (Hally 1983; Skibo

1992), and this needs to be linked to the analysis of fireplaces, hearths and ovens, and the useof archaeobotanical, faunal and residue-analysis to identify both the fuels that are being used

and the foods that were being prepared.

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SAND, SHELLS, FEATHERS AND WOODS: EMIC AND ETIC PERSPECTIVES

Feathers ends his paper by critiquing Woods(1986) call for a more emic approach. However,

I feel that the message of Woods has been misunderstood: to understand the intention of her

paper we need to recall the context within which she was writing. Woods prepared her article inthe early 1980s, when it had become common to assert that Inclusions in the pot fabric which

have low coefficient of thermal expansion, or one similar to that of fired clay (for example

grog, calcite, feldspars) should prove most resistant to the effects of thermal shock, whereas a

material such as quartz, with its large volume expansion when heated, should be detrimental

(Woods 1986, 157). Woods was partly responding to the work of Rye (1976) and Steponaitis

(1983), who had both used data from ceramic engineering to draw attention to the potential

problems of quartz inversion, and suggesting that in the case of Papua and Moundville quartzite

sand was abandoned in preference for shell-rich beach sand or shell temper because of its greater

thermal shock resistance. Woods cited Grimshaws (1971) speculation that reversal of the cool-

ing of quartz inversion of the phase transition after firing causes voids around quartzparticles (cf., Jacobs 1983), but she was writing prior to Freestones (1989) and Kilikoglou

et al.s (1995) suggestion that these microvoids help to dissipate the energy of external forces

resulting in the deflection, bifurcation and arrest of cracks, and that for this reason quartz actually

offers greater thermal shock resistance than grog does (West 1992, referenced in Tite et al.,

p. 316). In this academic context, the paper by Woods provided a necessary caution: the archaeo-

logical material from Britain contradicts most of the current theories concerning thermal shock

resistance properties of pottery(Woods 1986, 170). Contrary to the prevalent understanding of

ceramic engineering principles, which many archaeologists in the 1970s and 1980s were referen-

cing in their work, for some two thousand years most of the cooking pots made in Britain were

flat-based and tempered with quartzite sand. So, Woods (1986, 170) cautioned those who tooktheories which are relevant to high-fired, fine-bodied ceramics and applied them to low-fired,

coarse-bodied ancient ceramicsand suggested that the etic approach should be used with a

little more discretion and more frequently in conjunction with emic data: if this is done it may

once again become a useful method for determining the technology and function of archaeo-

logical ceramics and the motives of potters in the past(Woods 1986, 170). Woods was arguing

the need to maintain a careful balance between developing our modern, scientific (etic), analysis

of material constraints and using the ancient, archaeological (emic) evidence of what the potters

and consumers actually did. Experimental archaeology provides us with a vehicle through which

we can make an assessment of the formal and material properties of particular pottery forms and

fabrics and compare these with the specific archaeological evidence about how pots were madeand what they were used for. We should be careful not to let our modern expectations of how

materials respond to certain conditions, or our assumptions of continual progress in ceramic

technology, divert us from appreciating the empirical data of the archaeological remains. How-

ever, we can only do this effectively if we make some attempt to consider the context of the

potters and the cooks themselves. The question that we should be asking is not How effective

is quartz-tempered pottery at resisting thermal shock?butgiven that relatively thick-walled,

flat-based, quartz tempered cooking pots were made in BritainWhat were the cooking

methods and wider cultural concerns in Neolithic Britain that encouraged their production? and

What do geographical and temporal variations in the form, fabric and use of these pots tell us

about the relationship between pottery production and cooking methods within these societies?In describing Vincas Steponaitis(1984) work on Moundville pottery, Tite et al. summarize

this by stating that the use of coarsely ground shell during the Mississipian period provided the


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178 J. K. Feathers

most appropriate temper for cooking pots and that the use of shell temper can be seen as the

final stage in a technological development aimed at achieving the ideal cooking pot (Tite

et al., p. 319) However it is worth reminding ourselves of Warren DeBoers original comment

on Steponaitis paper: The thing that bothers me is that you have two thousand years of

ceramics, and you interpret these in a progressive way, as if potters are almost asymptomaticallyapproaching the perfect solution. I have a much more creative picture of human behaviour.

Instead of viewing this as an approach to an ideal solution, we should consider all the other

things which are going on in each stage . . . each thing makes sense in its own time, rather than

being directed towards any future (shell) solution, which is 2000 years ahead (DeBoer, in

Steponaitis 1984, 1267). As van der Leeuw has argued, we need to combine both an ana-

lytical perspective with a (re-)creative perspective in which the ceramicists who wish to

understand the pottersdecision-making will have to travel backin time and look forwardwith

those whom they study(van der Leeuw 1991, 13): the (re-)creative approach would stress the

uniqueness of each situation and the historical trajectory that has led to each situation(van der

Leeuw 1991, 21). However, van der Leeuw (1991, 21) ends this sentence by stating that thisapproach would deny the usefulness of universals or laws or lawlike generalizations, but I

think there is a major role for identifying universals with regard to the material properties

(see below).

EXPERIMENTAL ARCHAEOLOGY: UNIVERSALS AND LOCALS

Surprisingly, there has been very little general or theoretical discussion about the purpose

of experimental work in archaeology, perhaps because many experiments are of the one-off

weekendtype (Schiffer et al. 1994) or are aimed mainly at educating schoolchildren or at re-

construction eventsstaged for television (cf., Stone and Plane 1999). Michael Schiffer, JamesSkibo and the laboratory for traditional technology has probably done more to develop an

explicit agenda for experimental work than most (e.g., Schiffer et al. 1994: but see also Coles

1973; Reynolds 1979; Bell et al. 1996). But there remains a need for more explicit discussions

of the wider aims of experimental work, including the relationship between reconstructions

undertaken in the fieldand more controlled laboratory analysis. True scientific experiments do

not try to replicate real life: instead, they isolate and control a small number of variables to

assess how they interact in specified conditions. [Note that this is a somewhat different emphasis

to the description of experimental archaeology given by Coles (1973), where he places greatest

emphasis on using materials and techniques available at specific locations and time periods.]

Although experimental archaeology is directed at understanding how people have made andused artefacts within past societies, it has been largely concerned with measuring physical and

chemical changes in materials brought about by artefactartefact interactions. On its own, such

work is a poor area for exploring the social, economic or ideological significance of material

culture, but the results of this research are essential for a better understanding of how materials

respond to particular conditions created by people in the past, as well as some aspects of the

foresight and organization that were necessary to produce specific results.

Archaeologists have made good use of the extensive research on the material properties of

ceramics that has been done for industry, and this has provided the foundation for much of our

understanding of the general principles of how the properties of natural clays can be altered by

adding and subtracting other materials and by the firing conditions (e.g., Shepherd 1965; Rice1987). But ceramic engineers rarely consider low-fired ceramics with large amounts of coarse

tempering materials or their use for activities such as cooking over an open fire (cf., Woods

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1986, 170; Bronitsky 1989, 591). This is one of the reasons why archaeologists need to create

their own experimental programmes.

This leads to the question of which materials and methods should be used by experimental

archaeologists who are seeking to gain a better understanding of pottery production and use in

the past. Some archaeological experiments can be undertaken on original ancient materials, andthis will have the benefit of authenticity when dealing with specific local questions. However,

archaeological materials may have changed their material properties through previous use,

re-use and long-term burial, and there is a reluctance to use original archaeological samples that

are a unique and valuable resource. It may be considered acceptable to use destructive analysis

to describe and identify the materials and methods used to make ancient ceramics, but only in

rare circumstances will it be possible to undertake an extensive research programme into their

mechanical properties. This is one of the reasons why most experimental work involves either

replicative studies (that deliberately try to mimic the fabric and form of ancient artefacts), or

they go one step further in researching the interrelationships between a restricted number of

variables involved in ancient technologies. The latter approach is the type of work that providesthe basis for the review by Tite et al. (2001), and it allow researchers to assess the effect of

changing one variable at a time. This means that other variables (e.g., clay type, percentage of

inclusions, firing temperature and so on) should ideally be kept constant, and this requires the

preparation of a wide range of samples for testing, and the development of specific experi-

mental machinery and expertise (Schiffer et al. 1994). Even if the intention is to use complete

vessels rather than briquettes, there is a problem because many traditional pottery-making

techniques result in relatively poor mixing of the fabric, variable wall thickness, and poor

temperature and oxidation control during firing: although the resulting pots are perfectly ser-

viceable, they would not be considered as sufficiently predictable standards for precisely

measured experiments. Thus Schiffer et al. (1994) developed a complex forming techniqueusing standardized extruded coils and plaster moulds, in order to promote uniformity in the

vessels that they tested.

There is a difference between experiments directed towards elucidating one area of techno-

logical change in a specific cultural context and researching a more general understanding of

ceramic technology and the universalproperties of specific materials. To date, most experi-

mental archaeology has been predicated by questions relating to specific technologies relating

to specific time periods or archaeological cultures, so that even where the relationship between

a small number of variables is measured in well controlled laboratory experiments, the para-

meters of the analysis are usually formulated and restricted by this framework (Tite et al.,

p. 310). Even within the current discussion, no consideration has been given to the role ofcoarse-tempered ceramics as a refractory material used for kiln linings and crucibles, which are

repeatedly raised to temperatures over 1000C and cooled again, but the literature on this topic

(e.g., Freestone 1989) may be very relevant to the current discussions. What is notable about

Tite et al.s review of previous workand, more specifically, their proposal for extending this

research beyond quartz-tempered pottery . . . to include other temper types . . . [and] . . . to cover

the range 6001000C (Tite et al., p. 321) and the promotion of standardized experimental

methodsis that it aims to create a more comprehensive data set that would be more univer-

sally applicable. This does not mean that the cultural significance of these properties will be the

same universally. Because technical choices affect more than one performance characteristic,

the same technical choice . . . can play quite different roles in different technologies(Schifferand Skibo 1987, 616). Moreover, a given technical choice may have rather different functions

at different times in a technologys history (Schiffer et al. 1994, 211). But if archaeologists


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180 J. K. Feathers

take care to analyse the specific forms, wear patterns and contextual data in order to reconstruct

what activities their vessels were used for, they would then be able to draw upon a relevant data

set of the material properties of different fabrics in order to re-assess how these would affect

the material properties of the fabrics that they are analysing in relation to the specific archaeo-

logical context concerned. It is only in relation to specific archaeological contexts, including ananalysis of the way in which the pots were used, that we can assess whether or not changes in

ceramic technology were due to a desire to achieve specific mechanical and thermal properties

that were beneficial in use(Tite et al., p. 317). The use of experimental archaeology to develop

a better understanding of the universal material properties of ceramic fabrics will not remove

the need for experiments designed to explore questions relating to specific local fabrics, and

local culinary techniques, based on specific archaeological evidence. However, the review

article by Tite et al. seems to represent a more encompassing vision for the role of experimental

archaeology, and I very much hope that their suggestion that there is a need to coordinate an

extensive series of experiments into the strength, toughness and thermal shock resistance

of diverse mixes of clays and tempers, fired under different conditions of temperature andoxidation, is acted upon.

ACKNOWLEDGEMENTS

I would like to thank Mike Tite for encouraging me to write this commentary, and Marcos

Martinon-Torres for discussing an earlier version with me.

REFERENCES

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REPLY

M. S. TITE

Research Laboratory for Archaeology and the History of Art, University of Oxford, 6 Keble Road, Oxford OX1 3QJ, UK

V. KILIKOGLOU

Laboratory of Archaeometry, Institute of Materials Science, NCSR Demokritos, Aghia Paraskevi, 15310 Attiki, Greece

and G. VEKINIS

Advanced Ceramics Laboratory, Institute of Materials Science, NCSR Demokritos, Aghia Paraskevi, 15310 Attiki, Greece

Feathers, in commenting on the paper by Tite et al. on the mechanical and thermal properties

of ancient ceramics, considers one particular aspect only; that is, the significance of the rise inthe frequency of shell temper in pottery produced in eastern North America during the later

prehistoric period.


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182 J. K. Feathers

The discussion of this rise in frequency of shell temper is systematic and well balanced, with

each of the possible explanations, other than the increased toughness and thermal shock resist-

ance associated with shell temper, being carefully considered and, in turn, rejected. As a result,

Feathers claims that the improved mechanical and thermal properties explanation remains a

possibility. However, he accepts that even if improved mechanical and thermal properties is theexplanation for the introduction of shell temper in the specific region under consideration (i.e.,

south-east Missouri), this explanation would not necessarily be applicable even to other parts of

eastern North America. Instead, since many factors can influence technological choice, each

situation must be considered in its own right.

However, the chronological link established between the introduction of maize agriculture

and shell-tempered pottery is impressive, and some common reason for this link across eastern

North America seems probable. The common reason proposed by Feathers is that the clearance

associated with the introduction of maize agriculture resulted in the availability of a new fuel,

and that the use of this new fuel resulted in the observed increase in reduction firing. In turn,

reduction firing delayed the decomposition of the shell carbonate and this facilitated theproduction of shell-tempered pottery, with its improved mechanical and thermal properties.

In contrast to Braun (1983), Feathers does not go on to argue that improved mechanical and

thermal properties were necessary for cooking maize; nor does he suggest that the use of shell

temper was the final stage in a 2000-year technological development, as implied by Steponaitis

(1983) and highlighted by Sillar. However, even if this fuel-based explanation for the link

between the introduction of maize agriculture and shell temper is correct, it is still possible that

shell-tempered cooking pots were favoured for some other reason than their improved mechan-

ical and thermal properties. We believe, therefore, that it would be valuable to investigate the

possible differences in taste between maize cooked in shell-tempered vessels and that cooked in

vessels tempered with quartz sand or grog.Furthermore, we are uneasy about the extent to which Feathers plays down, or even rejects,

the role of technological style in determining technological choice. As a result, we feel that he

does not take sufficient account of the possible wider cultural reasons for technological choice

in general, and for the link between the introduction of maize agriculture and shell-tempered

pottery across eastern North America in particular.

Schiffer comments on two aspects of the terminology used by Tite et al. First, he questions

the use of the term technological choicerather than technical choiceand, second, he high-

lights the clear difference between the physical or material properties of an artefact and its

performance characteristics in use.

Although we understand the need to distinguish between the choices made by the pottersduring production and the choices made by the consumers, for example, in selecting pots at a

market, like Sillar, we still prefer to retain the term technological choice for the former. In

part, this preference is because the term technological choice links in better with the term

technological change, which is routinely used (including by Schiffer in his final paragraphs)

when considering changes made by the artisans in their methods of production.

Conversely, we fully accept the very real difference between physical or material properties

and performance characteristics and we regret any ambiguity that exists in Tite et al. Certainly,

this difference is clearly expressed in both the discussion and in figures included in Tite (1999,

2001) and in Kilikoglou and Vekinis (2002).

Sillar makes a number of important points, with many of which we are in agreement. Thus,we agree that it is important, in each specific situation, to understand how a cooking pot was

used and to question the validity of standard laboratory strength, toughness and thermal shock

182 M. S. Tite et al.


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resistance measurements in providing a realistic measure of these properties in use. However,

because of the interdependence of the different properties, thermal shock resistance need not be

determined from unrealistic rapid quenching experiments, but can instead be inferred from the

more appropriate standard toughness measurements. Furthermore, we would agree that, when

measuring mechanical and thermal properties, it is essential to take into account the progressivedegradation of a cooking pot during use. However, since the internal surfaces of cooking pots

need to be sealed in order to minimize permeability of water and hence evaporation from the

outer surfaces (Schiffer 1990), data resulting from mechanical and thermal property measure-

ments on dry bodies should be valid.

Regarding the problem of lime spalling, it is important to distinguish between limited spalling

that only affects the appearance of a vessel, and would not therefore have been a problem in the

context of cooking pots, and the complete disintegration of a vessel that can occur immediately

after firing when there has been decomposition of the shell carbonate.

In conclusion, we would first emphasize that, in order to be able to infer realistically the

mechanical and thermal properties of the archaeological pottery under consideration, i

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