Porcelain

Such methods might including comparative techniques, expert opinion and the evaluation of written and verbal records, where these are available. Although there has historically been little or no gene flow between some human populations such as the aboriginal Australians and black Africans, they a. It is however widely held that at best, testing can only be of use when combined with other, more traditional, methods for helping to establish provenance. Cultural anthropologists believe humans to be monotypic because they argue races gradually fade into one another in many parts of the world. Other tests can be used to determine the composition of glazes and body materials, for comparison with the results of analyses carried out on reference specimens of known provenance. Opponents of racial groupings argue that a distinct difference is only one of the two conditions for racial classifiction; the second condition is a lack of significant gene flow between populations. For this reason the test is rarely used for dating finely-potted, high-fired ceramics. 2004).

The test is carried out on small samples of porcelain drilled or cut from the body of a piece, which can be risky and disfiguring. To complicate matters further, recent analyses suggest that everyone living today has exactly the same set of genealogical ancestors who lived as recently as a few thousand years in the past, although we have received our genetic inheritance in different proportions from those ancestors (Rohde et al. The most widely-known test, the thermoluminescence test (TL-test) can be used to provide an estimate, within very wide limits, of the date of last firing. Furthermore, the exponentially increasing number of our ancestors makes ancestry a quantitative rather than qualitative trait—5 centuries (or 20 generations) ago, each person had a maximum of >1 million ancestors (Ohno 1996). The value of testing in the authentication of Chinese porcelain is disputed. Misattributed paternity or adoption can separate biogeographical ancestry from socially defined ancestry. A few examples are given below. 2003).

However, fakes and reproductions have also been made at many times during the long history of Chinese ceramics and continue to be made today in ever-increasing numbers. In one series of focus groups in the state of Georgia, 40% of ∼100 respondents said they did not know one or more of their four grandparents well enough to be certain how that person(s) would identify racially (Condit et al. Whilst ceramics with features thus borrowed might sometimes pose problems of provenance, they would not generally be regarded as either reproductions or fakes. When asked about the ancestry of their parents and grandparents, many people cannot provide accurate answers. Chinese potters have a long tradition of borrowing design and decorative features from earlier wares. Despite its seemingly objective nature, ancestry also has limitations as a way of categorizing people (Elliott and Brodwin 2002). The piece would have been fired in a saggar (a lidded ceramic box intended to protect the piece from kiln debris, smoke and cinders during firing) in a reducing atmosphere in a wood-burning egg-shaped kiln, at a temperature approaching 1350 degrees Celsius. 2004).

The potting is good and the porcelain body is finely textured, indicating the presence of a significant proportion of China clay in the paste. However, others argue that low levels of differentiation between groups merely make the assignment to groups more difficult, not impossible (Bamshad et al. The decoration, a sage in a landscape of lakes and mountains with blazed rocks is typical of the period. The existence of allelic clines has been offered as evidence that individuals cannot be allocated into genetic clusters (Kittles & Weiss 2003). The translucent body showing through the clear glaze is of great whiteness and the cobalt decoration, applied in many layers, is of a fine blue hue. This phenomenon is often seen as a cline of allele frequencies. The tea caddy illustrated shows many of the characteristics of blue and white porcelain produced during the Kangxi period. As a result, allele frequencies will be correlated between these groups.

Starting early in the fourteenth century, blue and white wares rapidly became the main product of Jingdezhen, reaching the height of its technical excellence during the later years of the reign of the Kangxi emperor and continuing in present times to be an important product of the city. Populations from neighboring geographic regions typically share more recent common ancestors. It is of interest to note that a Yuan funerary urn decorated with underglaze blue and underglaze red and dated 1338 is still in the Chinese taste, even though by this time the large-scale production of blue and white porcelain in the Yuan, Mongol, taste had started at Jingdezhen. However, the study of intra-continental ancestry may require a greater number of informative markers. In 1975 shards decorated with underglaze blue were excavated at a kiln site in Jiangxi and, in the same year, an underglaze blue and white urn was excavated from a tomb dated to the year 1319, in the province of Jiangsu. Genetic techniques that distinguish ancestry between continents can also be used to describe ancestry within continents. In 1970 a small fragment of a blue and white bowl, also dated to the eleventh century, was also excavated in the province of Zhejiang. population.

In 1957 excavations at the site of a pagoda in the province Zhejiang uncovered a Northern Song bowl decorated with underglaze blue and further fragments have since been discovered at the same site. They conclude that ancient ancestry, which correlates tightly with self-described race and not current residence, is the major determinant of genetic structure in the U.S. It has been suggested that the shards originated from a kiln in the province of Henan. (2005) identified 4 genetic clusters among 3,636 individuals sampled from 15 locations in the United States, and were able to correctly assign individuals to groups that correspond with their self-described race (white, African American, East Asian, or Hispanic) for all but 5 individuals (an error rate of 0.14%). No complete piece of Tang blue and white is known to exist, but shards dating to the eighth or ninth century have been unearthed at Yangzhou in Jiangsu province. Using 326 genetic markers, Tang et al. It is believed that underglaze blue and white porcelain was first made in the Tang Dynasty. Nevertheless, recent research indicates that self-described race is a near-perfect indicator of an individual's genetic profile, at least in the United States.

After the decoration has been applied the pieces are glazed and fired. Without the use of genotyping, this has been approximated by the self-described ancestry of an individual's grand-parents. The blue decoration is painted onto the body of the porcelain before glazing, using very finely ground cobalt oxide mixed with water. In this context, it is becoming more commonplace to describe "race" as fractional ancestry. Following in the tradition of earlier qingbai porcelains, blue and white wares are glazed using a transparent porcelain glaze. Likewise, many white Americans have mixed European and African ancestry, where ~30% of whites have less than 90% European ancestry. The rims of such wares were left unglazed but were often bound with bands of silver, copper or lead. (2003) found that on average African Americans have ~80% African ancestry.

Though not the case with the bowl illustrated, many Song and Yuan qingbai bowls were fired upside down in special segmented saggars, a technique first developed at the Ding kilns in Hebei province. Shriver et al. The glaze and the body of the bowl would have been fired together, in a saggar, in a large, wood-burning dragon-kiln or climbing-kiln typical of southern kilns of the period. For example, self-described African Americans tend to have a mix of West African and European ancestry. The body is white, translucent and has the texture of very fine sugar, indicating that it was made using crushed and refined China stone, rather than a mixture of China stone and China clay. Some racial or ethnic groups, especially Hispanic groups, do not have homogenous ancestry. The bowl has incised decoration, probably representing clouds or the reflection of clouds in the water. One cause of the reduced power of the assignment of individuals to groups is admixture.

The Song dynasty qingbai bowl illustrated was probably made at the Jingdezhen village of Hutian, which was also the site of the Imperial kilns established in the year 1004. However, in analyses that assign individuals to group it becomes less apparent that self-described racial groups are reliable indicators of ancestry. Bowls, some with incised or moulded decoration and varying from the everyday to more finely made pieces represent the overwhelming bulk of surviving qingbai wares. (2005) were able to assign 1,048 individuals from 52 populations around the globe to one of six genetic clusters, which correspond to major geographic regions. When applied over a white porcelain body the glaze produces a greenish-blue colour that gives the glaze its name (qingbai in Chinese means greenish-blue). For example, using 993 markers, Rosenberg et al. The qingbai glaze is clear, but contains iron in small amounts. However, even if group identity is stripped and group identity assigned a posteriori using only genetic data, population structure can still be inferred.

The qingbai glaze is a porcelain glaze, so-called because it was made using China stone, an important constituent of the porcelain body. Many such studies are criticized for assigning group identity a priori. Qingbai wares were made at Jingdezhen and at many other southern kilns from the time of the Northern Song until their almost complete eclipse, starting early in the fourteenth century, by underglaze-decorated blue and white wares. These studies usually find that groups of humans living on the same continent are more similar to one another than to groups living on different continents. One advantage gained by the addition in varying amounts of China clay was that the composition of the mix could be varied to suit the position that the wares made from it would occupy in the kiln, with a clay-rich mix being used for wares to be fired at the hot end of the kiln and a stone-rich mix being used for wares to be fired at the cooler end of the kiln. The inference of population structure from multilocus genotyping depends on the selection of a large number of informative genetic markers. The temperatures within a typical large, southern egg-shaped kiln varied greatly, from hot, at the firebox end, to cooler, at the chimney end. Genetic data can be used to infer population structure and assign individuals to groups that often correspond with their self-identified geographical ancestry.

China clay when added to the body material produced a porcelain of great strength and whiteness (whiteness, in particular, was a much sought after property of porcelain, especially that used for blue and white wares). 2005), but in an unknown percentage of cases, they do not (Brodwin 2002; Kaplan 2003). Porcelain bodies made from China stone fire at a lower temperature, in the region of 1200 degrees Celsius, than those made with a mixture of China clay and China stone, which require firing in the region of 1350 degrees Celsius. At least among those individuals who participate in biomedical research, genetic estimates of biogeographical ancestry generally agree with self-assessed ancestry (Tang et al. During the Song and Yuan dynasties porcelain was made at Jingdezhen and other kiln sites in southern China using crushed and refined China stone alone, but by the early eighteenth century China clay was being added to the China stone, in about equal proportions. census prior to 1960; it can be identified by an individual from a list of possibilities or with use of terms drawn from that person's experience; or it can be calculated from genetic data by use of loci with allele frequencies that differ geographically, as described above. In northern China, high-fired, translucent porcelains were made at kilns in the provinces of Henan and Hebei. Ancestry can be ascribed to an individual by an observer, as was the case with the U.S.

These included the well-known Tang lead-glazed sancai (three-colour) wares, the high-firing, lime-glazed Yue celadon wares and low-fired wares from Changsha. The definition of ancestry may recognize a single predominant source or multiple sources. During the Sui and Tang periods (581 to 906) a wide range of ceramics, low-fired and high-fired, were produced. Ancestry may be defined geographically (e.g., Asian, sub-Saharan African, or northern European), geopolitically (e.g., Vietnamese, Zambian, or Norwegian), or culturally (e.g., Brahmin, Lemba, or Apache). However, Chinese experts emphasise the presence of a significant proportion of porcelain-building minerals (China clay, China stone or a combination of both) as an important factor in defining porcelain and shards recovered from Eastern Han kiln sites in Zhejiang, estimated to have been fired at a temperature of between 1260 to 1300 degrees Celsius, were found that met this condition. An alternative to the use of racial or ethnic categories is to categorize individuals in terms of ancestry. A strong body of Chinese scholarly opinion is currently of the view that the first true porcelain was made in the Chinese province of Zhejiang during the Eastern Han period, but this opinion is controversial. Furthermore, ethnic groups tend to promote marriage within the group, which creates an expectation of biological cohesion regardless of whether that cohesion existed in the past.

Claims have been made for the late Eastern Han period (100 to 200 AD) the Three Kingdoms period (220 to 280 AD) the Six Dynasties period (220 to 589 AD) and the Tang Dynasty (618 to 906 AD). Ethnic groups can share a belief in a common ancestral origin (Cornell and Hartmann 1998), which also can be a defining characteristic of a racial group. This in turn has led to confusion about when the first Chinese porcelain was made. Finally, despite attempts to distinguish "ethnicity" from "race," the two terms often are used interchangeably (Oppenheimer 2001). In the context of Chinese ceramics the term porcelain lacks a universally accepted definition. 2003). In 1743, during the reign of the Qianlong emperor, Tang Ying, the imperial supervisor at Jingdezhen produced a memoir entitled "Twenty illustrations of the manufacture of porcelain." Unfortunately, the original illustrations have been lost but the text of the memoir may be found here, together with photographs replacing the missing illustrations and an additional commentary. A researcher, clinician, or government official might assign an ethnicity to an individual quite different from the one that person would acknowledge (Kressin et al.

Père d'Entrecolles, explaining his motives for describing what he had seen at Jingdezhen, states that "Nothing but my curiosity could ever have prompted me to such researches, but it appears to me that a minute description of all that concerns this kind of work might, somehow, be useful in Europe" but in the event his first letter came too late to be of much help in the European search for the secret of making porcelain. Individuals might change ethnic groups over the course of their lives or identify with more than one group. He then goes on to describe the refining of China clay, kaolin or Gaoling, the preparation of glazes, the stages of forming porcelain wares, glazing and firing. Ethnic groups may come into existence and then dissipate as a result of broad historical or social trends. In his first letter, dated 1712, d'Entrecolles describes the way in which China stone was crushed, refined and formed into little white bricks known in Chinese as petuntse or baidunzi. 2001). Two letters written by Père Francois Xavier d'Entrecolles, a Jesuit missionary (and industrial spy) who lived and worked in Jingdezhen described in detail the methods and materials used in the manufacture of porcelain wares in the later years of the reign of the Kangxi emperor; an important period in the history of Chinese ceramics. Also, ethnicity, like race, is a malleable concept that can change dramatically in different times or circumstances (Waters 1990; Smelser et al.

Detailed descriptions of the manufacture of porcelain at Jingdezhen during the Qing dynasty exist, including, from the European perspective, the letters of Père d'Entrecolles and from the Chinese perspective, a memoir written by Tang Ying. Combining these groups into a single category may serve useful bureaucratic or political ends but does not necessarily result in a better understanding of these groups. In the year 1004, under the Song emperor Jingde, the newly re-named city of Jingdezhen was established as a centre for the production of imperial porcelain. In the United States, the ethnic group "Hispanic or Latino" contains such subgroups as Cuban Americans, Mexican Americans, Puerto Ricans, and recent immigrants from Central America (Hayes-Bautista and Chapa 1987). The early wares were low-fired but by the time of the Southern and Northern Dynasties (420 to 589) locally available raw materials were being used to produce a form of porcelain. First, ascribing an ethnic identity to a group can imply a much greater degree of uniformity than is actually the case. The city of Jingdezhen has been an important centre for the production of ceramics in southern China since at least the early Han Dynasty. However, as a way of understanding human groups, ethnicity also suffers from several shortcomings.

Chinese enamelled wares are also produced in this way, but the enamels are added after the first, high-temperature, firing and the pieces are sent for a second firing in a smaller, lower-temperature kiln. It may encompass language, diet, religion, dress, customs, kinship systems, or historical or territorial identity (Cornell and Hartmann 1998). In the high temperature of the kiln the body and the glaze are fused together to become one unit. Ethnicity typically emphasizes the cultural, socioeconomic, religious, and political qualities of human groups rather than their genetic ancestry. After the body of a piece is formed and finished it is air-dried, coated with a glaze, dried again and fired. As the problems surrounding the word "race" became increasingly apparent during the 20th century, the word "ethnicity" was promoted as a way of characterizing the differences between groups (Huxley and Haddon 1936; Hutchinson and Smith 1996). An unusual characteristic of Chinese porcelain is that in the main it is green-fired or once-fired, which is to say that the body and the glaze are fired together.
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One result of this is that the property of resonance carries greater weight than that of translucence in the Chinese classification of high-fired ceramic wares. If "races" is too freighted a term for these basic divisions of humanity then, according to these authorities, new, convenient, non-academic terminology free of spurious valuations of superiority and inferiority should be developed and deployed whether social sensitivities are ruffled or not. This can lead to confusion because, for example, in China no distinction is drawn between high-fired stonewares and porcelain. Recognition of these groups, and simple ways to refer to them, is especially important in fields like medical research and diagnosis because a rapidly growing list of genetic disorders and predispositions are strongly linked to race and ethnicity (not to geographical "populations"). The Chinese tradition recognises only two primary categories of ceramic, high-fired (ci) and low-fired (tao). The basal groups outside the clinal zones on these maps are summarized quite well by longstanding racial and ethnic appellations. In the Western tradition ceramics are primarily divided into the categories of earthenware, stoneware or porcelain, depending upon the composition of the body material and the temperature at which the ware matures into a stable crystaline matrix. This position recently received a boost from genetic studies at the molecular level which show characteristic allele signatures for the groups traditionally identified as the three major races (Africans, Asians and Europeans), resulting in maps that clearly delineate genetic clines (in which the clinal zones are a small part of the total).

In turn, this led to the development of coal-fuelled kilns suitable for the high-temperature firing of clay-rich wares in the north and wood-fuelled kilns more suitable for the lower-temperature firing of the stone-rich southern wares. They are not convinced by the substitution of the term "population" for the term "race" because it leads to a potentially harmful imprecision in communication (for example, when one could simply say 'white' (or "Caucasian") one is instead compelled to say something like "an individual of the western Eurasian population", and when that individual doesn't happen to currently reside in western Eurasia one must say "an individual whose ancestors were of the western Eurasian population"). Geological differences between the northern and the southern land masses have influenced the nature of the ceramic wares made in the two areas and, for example, in the north ceramic wares tend to have bodies made using mainly China clay, in the south ceramic wares tend to have bodies made using mainly China stone. Other anthropologists and human geneticists argue that race is indeed a valid and valuable concept and that those holding the opposite view allow their social consciences (laudable per se) to confuse and delay accurate interpretations and applications of empirical data. The two land masses were brought together by the action of continental drift, forming a junction that lies very approximately along the line of the present-day Yangtze river. Bouchard, Jr., Professor of Psychology, University of Minnesota. Present day China comprises two separate, and from the geological point of view, distinctly different, land masses: the northern and the southern. Louis; and Thomas J.

Chinese ceramic wares are often classified as being either northern or southern. Holloway, Professor of Anthropology, Columbia University; Arthur Jensen; Joseph Carroll, University of Missouri-St. In the case of throwing, compression is applied by the hand of the potter. A number of scientists have supported this currently controversial view, including Ralph L. This is of importance because most of the methods used for forming the body parts of ceramic pieces (throwing on a wheel, for example) depend upon the application of compression to align the platelets and increase the plasticity and workability of the clay mixture. Vincent Sarich and Frank Miele, in Race: The Reality of Human Differences, write that "racial differences in humans exceed the differences that separate subspecies or even species in such other primates as gorillas and chimpanzees" and that "race is a biologically real phenomenon with important consequences". China stone and China clay are both platy minerals, which is to say that they are composed to varying degrees of small platelets of high surface area (external and internal) and are capable of holding relatively large amounts of water. They claim that race researchers are often attacked as racists, even if they espouse liberal sociopolitical views and claim to be against racism.

China stone also occurs kaolinised to a greater or lesser extent. Some researchers believe the view that races do not exist is influenced by racial politics and political correctness, not science. China clay largely comprises the clay mineral kaolinite (Gaoling) and China stone, petunse (baidunzi) is a micaceous rock of variable composition whose componants include quartz and sericite. This definition requires that a subspecies be genetically differentiated due to barriers to genetic exchange that have persisted for long periods of time; that is, the subspecies must have historical continuity in addition to current genetic differentiation" Templeton (1998). Both minerals derive from the weathering and decomposition of granitic rocks. In most contemporary research, races are defined as evolutionary linages: "a subspecies (race) is a distinct evolutionary lineage within a species. Chinese porcelain is made using China stone, China clay or a combination of the two materials. They point to the existence of groups determined on the basis of multi-locus genetic analysis as evidence that human population structure does exist and to some extent resembles conventional definitions of race.

Firing. Firing is the operation of heating green (unfired) ceramic wares at high-temperatures in a kiln to make permanent their shapes. Some biologists believe that the view that races are a social construct or not biologically significant is incorrect. Wares glazed in this way are described as being green-fired or once-fired. 2003). In an alternative method of glazing particularly associated with Chinese and early European porcelains the glaze was applied to the unfired body and the two fired together in a single operation. Until the 2000 census, Latinos were required to identify with a single race despite the long history of mixing in Latin America; partly as a result of the confusion generated by the distinction, 42% of Latino respondents in the 2000 census ignored the specified racial categories and checked "some other race" (Mays et al. In common with many earlier wares, modern porcelain wares are often bisque-fired at around 1000 degrees Celsius, coated with glaze and then sent for a second glaze-firing at a temperature of about 1300 degrees Celsius, or greater. 2003).

Decoration. Porcelain wares may be decorated under the glaze, using pigments that include cobalt and copper, or over the glaze using coloured enamels. A person's racial identity can change over time, and self-ascribed race can differ from assigned race (Kressin et al. Many types of glaze, such as the iron-containing glaze used on the celadon wares of Longquan, were designed specifically for their striking effects on porcelain. Efforts to track mixing between groups led to a proliferation of categories (such as mulatto and octoroon) and "blood quantum" distinctions that became increasingly untethered from self-reported ancestry. Unlike their lower-fired counterparts, porcelain wares do not need glazing to render them impermeable to liquids and for the most part are glazed for decorative purposes and to make them resistant to dirt and staining. By the standards used in past censuses, many millions of children born in the United States have belonged to a different race than have one of their biological parents. Glazing. It generally supposed that the first glazes to appear on ceramic wares resulted from the unavoidable presence in the kiln of lime-rich wood ash, which acted on the surface of the wares as a flux. Efforts to sort the increasingly mixed population of the United States into discrete categories generated many difficulties (Spickard 1992).

However, the lesson should be well-learned; potters work within constraints set by the materials and methods that they use and these constraints cannot be overcome by the application of unfocused brute force. In other countries in the Americas where mixing among groups was more extensive, social categories have tended to be more numerous and fluid, with people moving into or out of categories on the basis of a combination of socioeconomic status, social class, ancestry, and appearance (Mörner 1967). The sight of a novice potter wrestling with an eccentric mass of rotating clay in an attempt to save both pot and face can produce mixed emotions in the minds of more experienced onlookers. The decennial censuses conducted since 1790 in the United States also created an incentive to establish racial categories and fit people into those categories (Nobles 2000). To the casual observer, throwing carried out by an expert potter appears to be a graceful and almost effortless activity, but this masks the fact that a rotating mass of clay possesses energy and momentum in an abundance that will, given the slightest mishandling, have a rapid and dramatic effect on the piece being thrown. An example is the "one-drop rule" implemented in some state laws that treated anyone with a single known African American ancestor as black (Davis 2001). However, the fast-wheel also brought with it significant problems and made new demands on the skills of the potter. In the United States, social and legal conventions developed over time that forced individuals of mixed ancestry into simplified racial categories (Gossett 1997).

The introduction of the fast-wheel brought benefits in the form of speed and a job that might have taken hours, or even days, to complete was reduced to one that could be done in minutes. 2003). Unlike hand-building, in wheel-throwing the bulk of the energy used does not come directly from the hands of the potter. university, ∼30% were estimated to have <90% European ancestry (Shriver et al. The wheel was wound-up and charged with energy by pushing it round with a stick, an arrangement that permitted the energy stored in the wheel to be finely directed to where it was required, at the point where the hands of the potter come into contact with the clay. In a survey of college students who self-identified as white in a northeastern U.S. This changed with the introduction of the fast-wheel, early forms of which utilised energy stored in the rotating mass of the heavy stone wheel itself. Similarly, many people who identify as European American have some African or Native American ancestors, either through openly interracial marriages or through the gradual inclusion of people with mixed ancestry into the majority population.

In the coiling method of construction, all of the energy required to form the body of a piece is supplied directly by the hands of the potter. 1998). The earliest ceramics were hand-built using a simple coiling technique in which clay was rolled into long threads that were then pinched and beaten together to form the body of a vessel. In the United States, for example, most people who self-identify as African American have some European ancestors—in one analysis of genetic markers that have differing frequencies between continents, European ancestry ranged from an estimated 7% for a sample of Jamaicans to ∼23% for a sample of African Americans from New Orleans (Parra et al. The process of throwing is in fact one of remarkable complexity. In the Americas, the immigrant populations began to mix among themselves and with the indigenous inhabitants of the continent. To the spectator, throwing is often seen as pulling clay upwards and outwards into a required shape and potters often speak of pulling when forming a piece on a wheel, but the term is misleading, clay in a plastic condition cannot be pulled without breaking. The immigrants to the New World came largely from widely separated regions of the Old World—western and northern Europe, western Africa, and, later, eastern Asia and southern and eastern Europe.

The relatively low plasticity of the clays used for making porcelain can cause difficulties for the potter, particularly in the case of wheel-thrown wares. In parts of the Americas, the situation was somewhat different. Sometimes a combination of these methods is used and, for example, it would not be uncommon for a piece to have a thrown body, moulded handles and slip-cast decoration, the parts being luted together before firing (lute is a thick liquid mixture of clay and water used to join unfired parts together). 54). Forming. Porcelain wares are formed by hand-building, moulding, pressing, slip-casting or by throwing on a potter's wheel. In the Old World, the gradual transition in appearances from one group to adjacent groups emphasized that "one variety of mankind does so sensibly pass into the other, that you cannot mark out the limits between them," as Blumenbach observed in his writings on human variation (Marks 1995, p. The Wikipedia article on Pottery provides much useful background information on methods used for forming, decorating, finishing, glazing and firing ceramic wares. Even as the idea of "race" was becoming a powerful organizing principle in many societies, the shortcomings of the concept were apparent.

The porcelain clay body, unfired or fired, is sometimes spoken of as the paste and porcelain clay is itself sometimes described as the body (for example, when buying materials a potter might order such an amount of porcelain body from a vendor). Moreover, they argue that biology will not explain why or how people use the idea of race: history and social relationships will. Reference should be made to the Wikipedia article on Pottery for an explanation of some of these terms, but it might be helpful to note that the material used to form the body of porcelain wares is often referred to as clay, even though clay minerals might account for only a small proportion of its whole. As such it cannot be a useful analytical concept; rather, the use of the term "race" itself must be analyzed. When referring to the materials that they use, potters often employ words and names in a way that can be confusing for the layman. Since the 1960s, some anthropologists and teachers of anthropology have re-conceived "race" as a cultural category or social construct, in other words, as a particular way that some people have of talking about themselves and others. Some clays used for making ceramic wares are too cohesive to be thrown on the wheel, including for example, the brown clays used to form the bodies of the red stonewares of Yixing in the Chinese province of Jiangsu and as a result of this Yixing-wares are almost always hand-built. In particular, populationists claim that:.

Thus, the range of water contents within which porcelain clays can be worked is very narrow and the loss or gain of water during storage and throwing or forming must be carefully controlled to keep the clay from becoming too wet or too dry to manipulate. The "populationist" view does not deny that there are physical differences among peoples; it simply claims that the historical conceptions of "race" are not particularly useful in accounting for these differences scientifically. Porcelain clays are of lower plasticity (shorter) than many other clays used for making pottery and wet very quickly, which is to say that small changes in the content of water can produce large changes in workability. Populations are, in a sense, simply statistical clusters that emerge from the choice of variables of interest; there is no preferred set of variables. In soil mechanics plasticity is determined by measuring the increase in content of water required to change a clay from a solid state bordering on the plastic, to a plastic state bordering on the liquid, though the term is also used less formally to describe the facility with which a clay may be worked. This substitution is not simply a matter of exchanging one word for another. Long clays are cohesive (sticky) and of high plasticity and short clays are less cohesive and are of lower plasticity. For example, some scientists developed the notion of "population" to take the place of race.

The clays used by potters are often described as being long or short according to plasticity. These developments had important consequences. Other materials mixed with China clay to make porcelain clay have included ball-clay, glass, bone ash, steatite, quartz, petuntse and alabaster. There can be as much difference between two ethnicities grouped into a single "race" as there can be between ethnicities grouped (often arbitrarily) into an another "race". The composition of porcelain is highly variable, but China clay, comprising mainly or in part the platey clay mineral kaolinite is often a significant component. Instead of classing people into one "group", say "Caucasians" or Europeans you have Britons, Frenchmen, Germans, Nords, western Slavs and Celts rather than having a term implying a (possible) ancestory group in the Caucasus which is definitely too distant for any real consideration, and moreover reaching to groups including eastern Slavs, Roma, as well as Georgians, and others who differ notably, both in culture, and to a noteworthy extent in physical appearance, from the aforementioned ethnic groups. However, ceramics have an existance that is entirely independent of the words used to classify them and in this article the term porcelain is taken to encompass a broad range of high-fired ceramic wares, including some that might according to some systems of classification fall into the category of stoneware. Some argue it is preferable when considering biological relations to think in terms of populations, and when considering cultural relations to think in terms of ethnicity, rather than of race.

Where this line is drawn depends upon how the terms porcelain and stoneware are defined and this puzzle has been and continues to be the subject of controversy. In much of Europe groups such as Roma and Turks are commonly defined as racially distinct from White Europeans, though these groups could be considered "Caucasian" by old physical anthropological methods which employed finite nose measurements as the standard form of racial classifaction. Another difficult line to draw is that which divides high-fired stonewares from porcelain. In the United States, in what is referred to as the one-drop rule, the term Black subsumes people with a broad range of ancestries under one label, even though many who are termed Black could be more accurately described as white through simple anthropologic or taxonomic method. Industrial and other uses are (or, it is hoped, will be) covered elsewhere in the encyclopedia. In Europe, such a distinction, suggesting that South Europeans are not European or white, would seem odd at least or possibly even insulting. This follows the Wikipedia policy of drawing a line between technology and the fine arts, though in the case of porcelain the line is a difficult one to draw. For instance in many parts of the United States, categories such as Hispanic or Latino are viewed to constitute a race, though others see Hispanic as a linguistic and cultural grouping coming from a variety of backgrounds.

Porcelain has many uses, but this article is concerned mainly with its employment as a material used to make objects of craft and fine art, including decorative and utilitarian household wares. In everyday speech, race often describes populations better defined as ethnic groups, often leading to discrepancies between scientific views on race and popular usage of the term. . For example, most babies born with Tay-Sachs in North America at present are not from Jewish families, despite stereotypes to contrary.
. This is fortunate, as increasing interracial marriage is reducing the predictive power of race. Its high resistance to the passage of electricity makes porcelain an ideal insulating material and it is used in dentistry to make false teeth, caps and crowns. As genetic tests for such conditions become cheaper, and as detailed haplotype maps and SNP databases become available, the need to resort to race should diminish.

Porcelain is used to make wares for the table and kitchen, sanitary wares, decorative wares and objects of fine art. Regardless of the name, a working concept of sub-species grouping can be useful, because in the absence of cheap and widespread genetic tests, various race-linked gene mutations (see Cystic fibrosis, Lactose intolerance, Tay-Sachs Disease and Sickle cell anemia) are difficult to address without recourse to a category between "individual" and "species". Physical properties associated with porcelain include those of low permeability, high strength, hardness, glassiness, durability, whiteness, translucence, resonance, brittleness, high resistance to the passage of electricity, high resistance to thermal shock and high elasticity. This may either be a matter of semantics, or an effect of an underlying cultural significance of race in racist societies. The curved shape of the upper surface of the Venus-shell resembles the curve of a pig's back (Latin porcella, a little pig, a pig). Even those who reject the formal concept of race, however, still use the word race in day-to-day speech. Porcelain was so-named after its resemblance to the white, shiny Venus-shell, called in old Italian porcella. Historians, anthropologists and social scientists often describe human races as a social construct, preferring instead the term population, which can be given a clear operational definition.

The toughness, strength and translucence of porcelain arises mainly from the formation at high temperatures within the clay body of the mineral mullite and glass. However, any given physical characteristic generally is found in multiple groups (Lahr 1996), and demonstrating that environmental selective pressures shaped specific physical features will be difficult, since such features may have resulted from sexual selection for individuals with certain appearances or from genetic drift (Roseman 2004). Porcelain clay when mixed with water forms a plastic paste which can be worked to a required shape or form that is hardened and made permanent by firing in a kiln at temperatures of between about 1200 degrees Celsius and about 1400 degrees Celsius. Considerable speculation has surrounded the possible adaptive value of other physical features characteristic of groups, such as the constellation of facial features observed in many eastern and northeastern Asians (Guthrie 1996). Porcelain is a hard ceramic substance made by heating at high temperature selected and refined materials often including clay in the form of kaolinite. 2003). ISBN: 087701 612 7. In Brazil, for example, skin color is not closely associated with the percentage of recent African ancestors a person has, as estimated from an analysis of genetic variants differing in frequency among continent groups (Parra et al.

Chinese Ceramics from the Percival David Foundation. Chronicle Books, San Francisco, n.d. 2004). Rosemary Scott and others, Imperial Taste. Furthermore, in some parts of the world in which people from different regions have mixed extensively, the connection between skin color and ancestry has been substantially weakened (Parra et al. ISBN: 07286 0265 2. Sub-Saharan Africans, tribal populations from southern India, and Indigenous Australians have similar skin pigmentation, but genetically they are no more similar than are other widely separated groups. Stacey Pierson, Earth, Fire and Water: Chinese Ceramic Technology. Percival David Foundation of Chinese Art, University of London, 1996. Because skin color has been under strong selective pressure, similar skin colors can result from convergent adaptation rather than from genetic relatedness.

Thames and Hudson, London, 1996. Evidence for this includes the finding that a substantial portion of the differences of skin color between Europeans and Africans resides in a single gene, SLC24A5 the threonine-111 allele of which was found in 98.7 to 100% among several European samples, while the alanine-111 form was found in 93 to 100% of samples of Africans, East Asians and Indigenous Americans (Lamason et al. The New Standard Guide. A leading hypothesis for the selection of lighter skin in higher latitudes is that it enables the body to form greater amounts of vitamin D, which helps prevent rickets (Jablonski 2004). He Li, Chinese Ceramics. 2001; Rees 2003). Such blue and white wares were not fakes or, in the main, convincing reproductions, even though some pieces carried four-character Kangxi reign-marks that continue to cause confusion to this day. Darker skin appears to be strongly selected for in equatorial regions to prevent sunburn, skin cancer, the photolysis of folate, and damage to sweat glands (Sturm et al.