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