Sansai glazed ware: covered jar.
Except for the Shosoin Sansai, green-glazed ceramics, which are the only examples of such color glazed ceramics from the Shosoin period, all of the remaining examples of sansai and green-glazed ceramics in Japan have been excavated from Nara and Heian period sites. The types of these sites are palaces, government offices, and other public offices. These sites include the remains of palaces, government offices, temples, shrines, ritual sites, tombs, villages, fences, old kilns, and many others. The types of ceramics with colored glazes include jars, bottles, bowls, plates, bowls, bowls, firehouses, pagodas, goji, inkstones, etc. The glazes are mainly based on lead glazes, as in the Shosoin three colors: green, yellow, and white three colors, green and white Nisai, green glaze, yellow glaze, white glaze, and others. However, these various types of vessels and glazes were not used uniformly throughout the Nara and Heian periods, and their combinations varied from period to period. As mentioned in the overview section, colorful glazed ceramics such as sansai (Sansai), nisai (Nisai), yellow glazed, and white glazed wares were used from the Nara period to the early Heian period, while Ryokuyu and single-color wares were used exclusively after that.
The colored-glazed ceramics used in the Nara period include several types of jars, such as large and small short-necked jars, five types of bottles, such as multibellied bottles, water jars, wide-mouth bottles, and long-necked bottles, two types of bowls, such as iron bowls and flat bowls, armoire plates, cups, and various special items, such as incense burners, fireplace steamer, kettles, saucers, pagodas, and inkstone. In addition to the five types of lead-based glazes (sansai, nisai, green, yellow, and white), there are also known to exist white glazes that do not contain lead at all, as recently discovered at the Kurotou site in Yamanashi Prefecture. In addition, except for the early examples, most of the painted glazed ceramics of the Heian period (794-1185) are monochrome Ryokuyu vessels. By vessel type, there are several types of jars, including short-necked spittoon jars and four-footed jars, five types of bottles, including two types of hand-formed bottles, small vases, flower vases, and wide-mouth bottles, two types of bowls and bowl-shaped bowls, three types of bowls, two types of vessels, and four types of dishes, as well as special types of goji, incense burners, and mud towers.
Where and how were these types of colored glazed ceramics produced? No ancient kiln sites have yet been discovered where colorfully glazed ceramics such as sansai and nisai were fired, including the Shosoin sansai ware. However, in the Shosoin document “Zobutsu Sho Sakurimonocho”, there is a section on zosai, and we can learn about its production methods during the Nara period. Dr. Toshio Fukuyama has revealed that this “Zobutsu-sho Sakubutsu-cho” is a record of the construction of the western main hall of Kofuku-ji Temple over a period of one year from 733. Although we do not have time to list the original text at this time, it describes the production process as follows. To make four 8″ diameter ceramic bowls and three thousand and one hundred 4″ diameter ceramic oil cups, 2,500 kilograms of potter’s clay was transported in five trucks from Kagano (near Hirakata, Osaka Prefecture), and 374 pieces of rubber for fuel were transported in 67 trucks from Yamaguchi (near the mountain behind Kasuga Grand Shrine), at a total cost of 22,000 yen per truck. In this case, it is not clear where and what kind of kiln was used for the firing, but it goes without saying that it was a government-run workshop. And the materials necessary to make the glaze were applied for and supplied to the government. According to the research of Dr. Kazuo Yamazaki, who examined the glaze manufacturing process from the materials listed in the report, graphite, or metallic lead, is first heated and melted to oxidize it to make ledan (lead oxide).
Then, white stone (quartz) is added as a tanning agent to produce lead silicate, a glaze with a composition similar to today’s lead glass. Adding greenish blue to this produces a green glaze, and adding red clay (clay with high iron content) produces a yellowish-brown glaze. When these three glazes are combined, a sansai (Sansai) glaze is produced. Glue was used as an adhesive to apply glaze to unglazed vessels, salt was used to grind lead into a fine powder, and boar fat was used to accelerate the oxidation of lead. Looking at the composition of the green glaze on the actual excavated pottery shards, those from the Nara period contain less lead oxide and more silicon dioxide, but the amount of lead oxide increases as the period progresses. It is also known that the amount of copper oxide is higher in older pieces and gradually decreases in the Heian period.
As seen in the Shosoin three colors, colored-glaze ceramics were fired using carefully selected clay, first fired at a temperature of around 1,000 degrees Celsius, and then glazed and oxidized at a lower temperature of 750 to 800 degrees Celsius. There are currently 25 known sites in the Kinai and Tokai regions where green-glazed ceramics were fired. Of these, only two date to the Nara period: the tile kiln site in the precincts of Toshodaiji Temple in Nara City and the tile kiln site in Nishi Kawarasaka, Kawakami-cho, Nara City (on the hill behind Todaiji Temple). The Kawarasaka kiln is noteworthy for its location, as the tiles and glaze are covered with fresh green glaze, and at the end of the 8th century, there is a group of tile kiln sites on the grounds of Yoshishibe Shrine in Suita City, Osaka Prefecture, which fired Ryokuyu tiles for the construction of Heian-kyo. At this time, green-glazed pottery kilns began to appear in Shiga and Wakayama prefectures and other areas around the Kinai region, and the production technology of colored-glazed pottery, which had been maintained at the center of the Kinai region, began to spread to the surrounding areas with the relaxation of the Ritsuryo (Law) system. In contrast, production in the Kinai region declined. In contrast, production in the Kinai region declined. It is known that articles on “Owari ao “瓷” found in ancient documents dating from the 10th century onward, such as “Saigu Ki”, “Kitayama Sho”, and “Eike Jiyo”, correspond to the distribution of Ryokuyu pottery kilns. In recent years, there has been a rapid increase in the number of examples of green-glazed ceramics excavated from various parts of Japan, the majority of which date to the 9th to 10th centuries, and many of them can be traced back to the place of production by their clay and glaze tone.
The most common examples are products from Narumi Kiln in Aichi Prefecture, which have thick light green glaze on yellowish-white clay, and products from Shinooka Kiln (Ohoku Kiln) in Komaki City, Aichi Prefecture, which have dark green glaze on grayish-black hard clay. Without even needing to look at ancient documents, we know that “Owari celadon” was superior to ceramics from other regions at that time, and was supplied to all regions of Japan.
How were the various types of colored glazed ceramics produced in this way used in those days? As mentioned above, there are many types of excavated sites of colored glazed pottery, but all of them are mainly sites related to rituals, and there is no evidence of their use in daily life. Recently, there has been an increase in the number of excavated cases of dwelling sites, but in most cases, these are those of villages attached to kokubunji temples or national offices, and are thought to have been used for special purposes or stored, and it is difficult to imagine that they were used as daily vessels. The use of these vessels can be divided into five main types, based on the nature of the remains. The first is a large short-necked jar with two types of glaze, sanshoku (Sansai) and green, found at the Ohbishima Ritual Site in Kasaoka City, Okayama Prefecture, where it was discovered in a burial mound as a cremation ware. A representative example with clear contents was discovered in 1963 on the southern slope of a hillside along the Yamato Highway in Kitanagoso, Takanokuchi Town, Wakayama Prefecture, and was a sancai jar with a rectangular slipstone stone chest with a lid shaped like a roof lid, 30 cm below ground level. The only other example of a small sansai jar used as a burial accessory in a tomb is the grave of Kojita Anmanpo at Tsuzukeno, Miyakojimura, Yamabe-gun, Nara Prefecture. This is the oldest known example, with a grave marker dated 729.
The second type of vessels used in rituals at strategic points of transportation were offerings to the gods, and these were mainly small sansai vases.
The most prominent examples are the ritual sites of Ohtobishima in Kasaoka City, Okayama Prefecture and Okinoshima in Munakata County, Fukuoka Prefecture. Ohtobishima is a small island in the middle of the Seto Inland Sea, and from the base of a long, narrow sandbar on the northeastern edge of the island, 13 small sansai jars with 13 lids and 7 bodies were discovered, along with a Chinese mirror and numerous vessels for offerings. Since this island is located in the center of the Seto Inland Sea, right at the point where the tides change from east to west, it is thought that these vessels were dedicated to the sea gods to pray for safe voyages when the central government officials were waiting for the tide on their way down to the western sea. Okinoshima Island is another site of the same type. The third form was used for rituals at palaces, government offices, and temples, and the most typical example of this type of vessel is the Shosoin sansai. The same type of colored glazed pottery has been found at the Heijo Palace site, and there are also quite a few known examples found at major temples in the Kinai region. The combination of vessel forms consists of a Sansai fireplace, a Sansai/niscolor vase, a Nisai Ryokuyu vase, and a Sansai/niscolor/Ryokuyu Buddhist bowl, with contents similar to those of the Shosoin Sansai combination. The fourth type of pottery used is a group of green-glazed ceramics found at Buddhist sites in the mid-to-late Heian period, and two combinations are known. The first is found at the Yagoto-do site in Nagoya City and at the Nantai Summit site in Nikko, Tochigi Prefecture, where green-glazed ceramics in various combinations, such as goji, bowls, plates, and vases, have been discovered along with various other artifacts. In the case of the Nantai summit site in Nikko, a variety of metal esoteric Buddhist ritual implements were found in abundance, and we can see a combination of esoteric Buddhist dandan ku in them. The green-glazed ceramics found in a section of the temple area of Sanno Haiji in Gunma Prefecture consisted of three green-glazed bowls, four plates, and a bronze mirror on an altar made of wooden planks in a 60-cm square section made of circular rubble, with a green-glazed handled water bottle, earthenware bowls, and plates placed beside it. This may be an example of an earth shizumigu. Similar vessels have been excavated at the Hiraide site in Nagano Prefecture and the Miura site in Ishikawa Prefecture, although their contents are unknown. There is also a special type of grave site known as Imakumano Sozan in Higashiyama-ku, Kyoto City, in which three green-glazed vases, nine bowls, and six plates were placed in a square arrangement of stones the size of a small child’s head. The fifth type of use is that of green-glazed bowls and plates from the late Heian period, which have been found inside the side-cavity stone chambers of kofun tumuli. A typical example is the Mishima tumulus in Hagi City, Yamaguchi Prefecture, where the first half of a yokoana-shiki stone chamber was reconstructed to create a separate stone enclosure in which two green-glazed dishes were placed as vessels for offerings. Other examples of burial mounds excavated from yokoana-shiki stone chambers include the Iwatsubo burial mound in Nishinose, Osaka Prefecture, and the Ichi burial mound in Gokasho Village, Shiga Prefecture, although the conditions of these burial mounds are unknown. The nature of these rituals is not clear, but the wide range of dates of the offerings makes them an interesting problem.
As described above, a general view of the use of colorful glazed ceramics in the Nara and Heian periods includes some unknown items, such as those excavated from village sites, but they are all closely associated with rituals, and there is no evidence of their use as daily vessels. As shown in the Shosoin document “Zobutsu Shokubutsu Shokubutsu-cho”, the production of colorfully glazed ceramics in the Nara period was a one-time event, as the materials necessary for the construction of the western hall of Kofukuji Temple were provided by the government and the ceramics were produced in the government workshop. It cannot be considered that the production was continuously carried out without a specific object. Furthermore, many of the vessels excavated from sites throughout Japan are of the same quality, such as the base and glaze tone, and were produced in the same place, so it is impossible to say that production was carried out freely in each region. In particular, the small sansai vases indicate the existence of rituals that were held several times during a relatively limited period of time, and we can see the central government’s centralized form in these vases.
As seen in the “Saigu Ki” and the “Jiake Yadama”, green-glazed ceramics were widely produced from the Kinai region to the Tokai region during the Heian period, and were used in court ceremonies such as the “Gogoge Ceremony” or as part of the ritual implements in esoteric Buddhist ceremonies. In those days, earthenware vessels were used as daily vessels. At that time, earthenware and Sue ware were used as daily vessels, and celadon and white porcelain imported from China were used as special high-end ceramics. In comparison, Nara-period colored glazed ceramics were soft and impractical for frequent use as daily vessels.
What then are the usage patterns of Tang Sancai, the origin of Japanese colored-glazed ceramics, and those of other regions? In China, since the Han Dynasty, green-glazed ceramics were usually buried in tombs as Ming vessels. In Tang Sancai, all known sites are tombs, and there are no clear examples from other sites that show a different form of use. On the other hand, in Bohai Sea, which existed in the eastern northeastern part of China for about 200 years since the end of the 7th century, green-glazed tiles and monstrous green-glazed pottery products were used in palaces in the Tokyo Castle, and sancai ware leg fragments were found along with daily vessels in pit dwelling sites in the outer city area. On the Korean peninsula, there are also known examples excavated from Baekje and Silla temple sites, all of which show similar conditions of use to those in Japan. However, the Islamic variety of glazed ceramics (Persian Sansai) in the west, which is a continuation of Tang Sansai, were used as everyday vessels for practical purposes. Thus, the use of colorful glazed ceramics differs from country to country. In the case of Japan, only the tomb of Kojita-Yamanpo was used as a burial accessory, while most of the others were used as ritual vessels, except for cremation vessels. This is a distinctive feature of Japanese colored glazed pottery.
