上海交通大学：《材料与文明》课程教学资源（参考资料）Understanding Mater_Chapter 15 - No Ceramics Age

15 No Ceramics s Age? 15.1.Ceramics and Civilization The utilization of ceramic materials by man is probably as old as human civilization itself.Stone,obsidian,clay,quartz,and min- eral ores are as much a part of the history of mankind as the prod- ucts which have been made of them.Among these products are tools,earthenware,stoneware,porcelain,as well as bricks,re- fractories,body paints,insulators,abrasives,and eventually mod- ern"high-tech ceramics"used,for example,in electronic equip- ment or jet engines.Actually,fired or baked ceramic objects are probably the oldest existing samples of handicraft which have come to us from ancient times.They are often the only archaeo- logic clues that witness former civilizations and habitats.More- over,there are scholars who believe that life took its origin from ceramics.And some ancient mythologies relate that man was cre- ated from clay.It might be of interest in this context that the He- brew word for soil,dirt,clay,or earth is "Adama."Taking all of these components into consideration,it might be well justified to ask why historians did not specifically designate a ceramics age. The answer is quite simple:stone,copper,bronze,and iron can be associated with reasonably well-defined time periods that have a beginning and frequently also an end during which these ma- terials were predominantly utilized for the creation of tools, weapons,and objects of art.In contrast to this,ceramic materi- als have been used continuously by man with essentially unbro- ken vigor commencing from many millennia ago until the pre- sent time.Thus,ceramics can be compared to a basso obstinato in a piece of music in which other instruments play the melody. Still,some identification of cultural stages through pottery is com- mon among historians and archaeologists,who distinguish a "pre- pottery"era from a pottery period.The latter one is classed by color,shape,hardness,and,notably,by decoration

15 The utilization of ceramic materials by man is probably as old as human civilization itself. Stone, obsidian, clay, quartz, and min￾eral ores are as much a part of the history of mankind as the prod￾ucts which have been made of them. Among these products are tools, earthenware, stoneware, porcelain, as well as bricks, re￾fractories, body paints, insulators, abrasives, and eventually mod￾ern “high-tech ceramics” used, for example, in electronic equip￾ment or jet engines. Actually, fired or baked ceramic objects are probably the oldest existing samples of handicraft which have come to us from ancient times. They are often the only archaeo￾logic clues that witness former civilizations and habitats. More￾over, there are scholars who believe that life took its origin from ceramics. And some ancient mythologies relate that man was cre￾ated from clay. It might be of interest in this context that the He￾brew word for soil, dirt, clay, or earth is “Adamá.” Taking all of these components into consideration, it might be well justified to ask why historians did not specifically designate a ceramics age. The answer is quite simple: stone, copper, bronze, and iron can be associated with reasonably well-defined time periods that have a beginning and frequently also an end during which these ma￾terials were predominantly utilized for the creation of tools, weapons, and objects of art. In contrast to this, ceramic materi￾als have been used continuously by man with essentially unbro￾ken vigor commencing from many millennia ago until the pre￾sent time. Thus, ceramics can be compared to a basso obstinato in a piece of music in which other instruments play the melody. Still, some identification of cultural stages through pottery is com￾mon among historians and archaeologists, who distinguish a “pre￾pottery” era from a pottery period. The latter one is classed by color, shape, hardness, and, notably, by decoration. No Ceramics Age? 15.1 • Ceramics and Civilization

288 15·No Ceramics Age? Beginning from early times,clay was of particular interest to man for a number of reasons.First,clay is abundantly found in many parts of the world,albeit in different compositions,quan- tities,and qualities.Second,clay is pliable if it has the right con- sistency (e.g.,water content).Third,the shape of an object made from clay is retained as long as it is not exposed to water for an extended period of time.Fourth,clay becomes hard when dried, for example,in the sun or near fires.A fifth and most important property of clay was eventually discovered in ancient times:clay permanently hardens to a virtually indestructible but brittle and porous material when heated above about 500C.At this tem- perature,an irreversible chemical reaction begins to take place which precludes the substance from returning to its original duc- tile state and makes it water-resistant.Moreover,the fired prod- uct is much less susceptible to environmental interactions than many metals and alloys such as iron.In primitive pottery- making the objects were placed in a shallow pit in the ground and the fire(using wood or dung)was built over them. Some early artifacts made of fired clay are at least 9,000 years old and consist mostly of pottery or building materials,such as bricks.Moreover,some figurines have been found (such as in French caves)portraying animals or human bodies.The oldest samples of baked clay include more than 10,000 fragments of statuettes which were found in 1920 near Dolni Vestonice, Moravia,in the Czech Republic.They portray wolves,horses, foxes,birds,cats,bears,or women with exaggerated female at- tributes(Figure 15.1).One of these prehistoric female figurines remained almost undamaged.It has been named the "Venus of Vestonice"and is believed to have been a fertility charm.Schol- ars date the statuette,which stands about 10 cm tall,as far back as 23,000 B.C.Much speculation has evolved about these frag- ments,which,incidentally,contain some mammoth bone ash in the clay.Specifically,one group of anthropologists proposes that the figurines served some divinational purpose and were designed to shatter in the fire (by wetting the clay)so that priests or shamans could foretell future events from the fragments.In any event,this practice apparently did not lead to the invention of pottery. A still earlier example for prehistoric pyrotechnology,dating back to about 50,000 B.C.,consists of ground-up iron oxide pow- ders which have been fired to yield various colors.Pigments of this kind,together with a lead oxide binder,have probably been used for millennia,for body painting and other decorations Unfired clay as building material was likewise rather common. In some cases,the mud was inserted between and around wooden

Beginning from early times, clay was of particular interest to man for a number of reasons. First, clay is abundantly found in many parts of the world, albeit in different compositions, quan￾tities, and qualities. Second, clay is pliable if it has the right con￾sistency (e.g., water content). Third, the shape of an object made from clay is retained as long as it is not exposed to water for an extended period of time. Fourth, clay becomes hard when dried, for example, in the sun or near fires. A fifth and most important property of clay was eventually discovered in ancient times: clay permanently hardens to a virtually indestructible but brittle and porous material when heated above about 500°C. At this tem￾perature, an irreversible chemical reaction begins to take place which precludes the substance from returning to its original duc￾tile state and makes it water-resistant. Moreover, the fired prod￾uct is much less susceptible to environmental interactions than many metals and alloys such as iron. In primitive pottery￾making the objects were placed in a shallow pit in the ground and the fire (using wood or dung) was built over them. Some early artifacts made of fired clay are at least 9,000 years old and consist mostly of pottery or building materials, such as bricks. Moreover, some figurines have been found (such as in French caves) portraying animals or human bodies. The oldest samples of baked clay include more than 10,000 fragments of statuettes which were found in 1920 near Dolní Veˇstonice, Moravia, in the Czech Republic. They portray wolves, horses, foxes, birds, cats, bears, or women with exaggerated female at￾tributes (Figure 15.1). One of these prehistoric female figurines remained almost undamaged. It has been named the “Venus of Veˇstonice” and is believed to have been a fertility charm. Schol￾ars date the statuette, which stands about 10 cm tall, as far back as 23,000 B.C. Much speculation has evolved about these frag￾ments, which, incidentally, contain some mammoth bone ash in the clay. Specifically, one group of anthropologists proposes that the figurines served some divinational purpose and were designed to shatter in the fire (by wetting the clay) so that priests or shamans could foretell future events from the fragments. In any event, this practice apparently did not lead to the invention of pottery. A still earlier example for prehistoric pyrotechnology, dating back to about 50,000 B.C., consists of ground-up iron oxide pow￾ders which have been fired to yield various colors. Pigments of this kind, together with a lead oxide binder, have probably been used for millennia, for body painting and other decorations. Unfired clay as building material was likewise rather common. In some cases, the mud was inserted between and around wooden 288 15 • No Ceramics Age?

15.1.Ceramics and Civilization 289 FiGURE 15.1.Baked clay fig- urine called the "Venus of Vestonice"found in 1920 in the Czech Republic.Approxi- mate age:23,000 B.C. structures.In other instances,pressed clay bricks formed in bas- kets were used (called adobe)which were sometimes fortified with straw.(This constitutes one of the first examples of the pro- duction of a composite material,that is,a technique to strengthen clay by fibers.)Additionally,asphalt from natural oil wells was sometimes used as mortar.However,buildings of this type were highly vulnerable to the weather.They easily crumbled and thus needed constant renewal (except for cliff-dwellings;see Plate 15.11).As a consequence,layers of settlements were often built on top of previous ones,creating a mound of occupation debris (called a tell or a tall).This is characteristic for ruins found in Mesopotamia.Mass production of bricks was not performed in this region until the sixth millennium B.C.,probably because of a shortage of fuel.Later,however,that is,in the sixth century B.C.,the buildings of Babylon utilized fired and glazed bricks(see Plate 15.5). As outlined above,pottery-making is one of the oldest forms of crafts.The resulting vessels are quite useful for storing prop-

structures. In other instances, pressed clay bricks formed in bas￾kets were used (called adobe) which were sometimes fortified with straw. (This constitutes one of the first examples of the pro￾duction of a composite material, that is, a technique to strengthen clay by fibers.) Additionally, asphalt from natural oil wells was sometimes used as mortar. However, buildings of this type were highly vulnerable to the weather. They easily crumbled and thus needed constant renewal (except for cliff-dwellings; see Plate 15.11). As a consequence, layers of settlements were often built on top of previous ones, creating a mound of occupation debris (called a tell or a tall). This is characteristic for ruins found in Mesopotamia. Mass production of bricks was not performed in this region until the sixth millennium B.C., probably because of a shortage of fuel. Later, however, that is, in the sixth century B.C., the buildings of Babylon utilized fired and glazed bricks (see Plate 15.5). As outlined above, pottery-making is one of the oldest forms of crafts. The resulting vessels are quite useful for storing prop- 15.1 • Ceramics and Civilization 289 FIGURE 15.1. Baked clay fig￾urine called the “Venus of Veˇstonice” found in 1920 in the Czech Republic. Approxi￾mate age: 23,000 B.C

290 15·No Ceramics Age? erty and dry food,for cooking,and for transporting water.Still, pottery-making is seldom found among nomadic tribes in par- ticular as long as natural materials,such as gourds,skins,and large leaves,can be found or when baskets can be woven for the above-mentioned purposes.Moreover,and most importantly, potters must live within the reach of their raw materials and their kilns.Finally,ceramic pots are heavy and might break during travel.It is therefore not surprising that the art of pottery did not commence or was not practiced at all locations of the world at the same time and with equal sophistication,even though the raw materials were certainly available.Instead,pottery-making has been mainly exercised in areas in which agriculture has been firmly established,that is,where the population was reasonably settled.It is interesting to know in this context that pottery ap- pears in the Americas approximately 5,000 years later than in the 'old world"and that glazes,as well as the potter's wheel,and fre- quently also the kiln,were not known there in pre-Columbian times. The discovery that fired clay objects are water-resistant and sturdy eventually led to a systematic development of kilns with permanent walls and open tops.Certain modifications on the out- lay of the kilns and the type of fuel used eventually allowed in- creasingly higher temperatures.This has been discussed already in Chapter 1 in the context of the interrelationship between pottery-making and copper-smelting. 15.2·Types of Pottery Pottery is broadly divided into vitrified ware and unvitrified ware, a distinction that is based on whether or not clay composition and firing temperature cause the clay to melt or fuse into a glassy (vitreous)substance.Earthenware is made from "earthenware clay"fired at relatively low temperatures,that is,between 800 and 1200C,depending on the raw material;see Plate 15.1.It is porous when not subsequently glazed (see below)and is rela- tively coarse and often red or buff-colored,even black after fir- ing.Bricks and other construction materials,such as tiles,as well as terra cotta vessels are the major products in this category. Earthenware was probably the earliest kind of ceramics that was made,dating back to about 7,000 or possibly 8,000 B.C.Speci- mens of this age were found,for example,in Catal Huyuk in Ana- tolia (today's Turkey). Because of its porosity,the water which is stored in vessels made of unglazed earthenware percolates eventually through the

erty and dry food, for cooking, and for transporting water. Still, pottery-making is seldom found among nomadic tribes in par￾ticular as long as natural materials, such as gourds, skins, and large leaves, can be found or when baskets can be woven for the above-mentioned purposes. Moreover, and most importantly, potters must live within the reach of their raw materials and their kilns. Finally, ceramic pots are heavy and might break during travel. It is therefore not surprising that the art of pottery did not commence or was not practiced at all locations of the world at the same time and with equal sophistication, even though the raw materials were certainly available. Instead, pottery-making has been mainly exercised in areas in which agriculture has been firmly established, that is, where the population was reasonably settled. It is interesting to know in this context that pottery ap￾pears in the Americas approximately 5,000 years later than in the “old world” and that glazes, as well as the potter’s wheel, and fre￾quently also the kiln, were not known there in pre-Columbian times. The discovery that fired clay objects are water-resistant and sturdy eventually led to a systematic development of kilns with permanent walls and open tops. Certain modifications on the out￾lay of the kilns and the type of fuel used eventually allowed in￾creasingly higher temperatures. This has been discussed already in Chapter 1 in the context of the interrelationship between pottery-making and copper-smelting. Pottery is broadly divided into vitrified ware and unvitrified ware, a distinction that is based on whether or not clay composition and firing temperature cause the clay to melt or fuse into a glassy (vitreous) substance. Earthenware is made from “earthenware clay” fired at relatively low temperatures, that is, between 800 and 1200°C, depending on the raw material; see Plate 15.1. It is porous when not subsequently glazed (see below) and is rela￾tively coarse and often red or buff-colored, even black after fir￾ing. Bricks and other construction materials, such as tiles, as well as terra cotta vessels are the major products in this category. Earthenware was probably the earliest kind of ceramics that was made, dating back to about 7,000 or possibly 8,000 B.C. Speci￾mens of this age were found, for example, in Catal Hüyük in Ana￾tolia (today’s Turkey). Because of its porosity, the water which is stored in vessels made of unglazed earthenware percolates eventually through the 290 15 • No Ceramics Age? 15.2 • Types of Pottery

15.2·Types of Pottery 291 walls and evaporates on the free surface,thus cooling the water in the container.For the same reason,terra cotta containers can- not be used for storing milk or wine.Examples of more recent unglazed earthenware include Chinese teapots,first made dur- ing the Ming dynasty,as well as red stoneware made in MeiBen (Germany)or by Wedgwood in England at the beginning of the eighteenth century A.D. In order to hermetically seal the pores of goods made of earth- enware,an additional processing step called glazing was intro- duced around or probably even before 3000 B.c.by the Egyp- tians.It involved the coating of the fired objects with a water suspension of finely ground quartz sand mixed with sodium salts (carbonate,bicarbonate,sulfate,chloride)or plant ash.This was followed by a second firing,during which the glassy particles fused into an amorphous layer.The second firing is often at a lower temperature,being just sufficient to fuse the glaze.Inci- dentally,the Egyptians also glazed beads and bowls made of steatite,a soft stone which could be easily shaped,drilled,and abraded.Another technique to produce beads involved hand- molding a mixture of crushed quartz with sodium salts and mala- chite (Plate 1.3),which was then fired. Two other types of glazes which have been applied to earth- enware are likewise several millennia old.One of them is a trans- parent lead glaze.Lead reduces the melting or fusion point of the glaze mixture,which allows the temperature of the second firing to be even lower.Lead glaze was invented in China during the Han dynasty (206 B.C.-A.D.200)and was subsequently widely used by many civilizations.However,some lead from the glaze on tableware may be leached by the food.It is believed that this poi- soned a large number of Roman nobility and thus contributed (together with the lead from water pipes)to the fall of the Ro- man empire.Lead glazing for tableware is outlawed today by many countries unless fritted glazes are utilized which convert lead into a nontoxic form. An alternative technique involves an opaque,white tin glaze which hides possible color blemishes,for example,from iron im- purities.Tin glazing was probably first discovered by the Assyr- ians who lived in Mesopotamia(today's Northern Iraq)during the second millennium B.C.It was utilized for decorating bricks but fell eventually into disuse possibly because of the sudden in- terruption of the tin supply,as explained already in Chapter 7. In the ninth century A.D.,tin glazing was reinvented and again extensively utilized in Mesopotamia.From there it spread to Italy via the Spanish island of Maiolica (Majorca),after which the product was later named (Plate 15.7).French earthenware

walls and evaporates on the free surface, thus cooling the water in the container. For the same reason, terra cotta containers can￾not be used for storing milk or wine. Examples of more recent unglazed earthenware include Chinese teapots, first made dur￾ing the Ming dynasty, as well as red stoneware made in Meißen (Germany) or by Wedgwood in England at the beginning of the eighteenth century A.D. In order to hermetically seal the pores of goods made of earth￾enware, an additional processing step called glazing was intro￾duced around or probably even before 3000 B.C. by the Egyp￾tians. It involved the coating of the fired objects with a water suspension of finely ground quartz sand mixed with sodium salts (carbonate, bicarbonate, sulfate, chloride) or plant ash. This was followed by a second firing, during which the glassy particles fused into an amorphous layer. The second firing is often at a lower temperature, being just sufficient to fuse the glaze. Inci￾dentally, the Egyptians also glazed beads and bowls made of steatite, a soft stone which could be easily shaped, drilled, and abraded. Another technique to produce beads involved hand￾molding a mixture of crushed quartz with sodium salts and mala￾chite (Plate 1.3), which was then fired. Two other types of glazes which have been applied to earth￾enware are likewise several millennia old. One of them is a trans￾parent lead glaze. Lead reduces the melting or fusion point of the glaze mixture, which allows the temperature of the second firing to be even lower. Lead glaze was invented in China during the Han dynasty (206 B.C.–A.D. 200) and was subsequently widely used by many civilizations. However, some lead from the glaze on tableware may be leached by the food. It is believed that this poi￾soned a large number of Roman nobility and thus contributed (together with the lead from water pipes) to the fall of the Ro￾man empire. Lead glazing for tableware is outlawed today by many countries unless fritted glazes are utilized which convert lead into a nontoxic form. An alternative technique involves an opaque, white tin glaze which hides possible color blemishes, for example, from iron im￾purities. Tin glazing was probably first discovered by the Assyr￾ians who lived in Mesopotamia (today’s Northern Iraq) during the second millennium B.C. It was utilized for decorating bricks but fell eventually into disuse possibly because of the sudden in￾terruption of the tin supply, as explained already in Chapter 7. In the ninth century A.D., tin glazing was reinvented and again extensively utilized in Mesopotamia. From there it spread to Italy via the Spanish island of Maiolica (Majorca), after which the product was later named (Plate 15.7). French earthenware, 15.2 • Types of Pottery 291