Fifth and Sixth Centuries
In the fifth century, increased travel between Japan and its Asian neighbors brought new technology to the archipelago. The oldest discovered iron furnaces date from this time period, as do kilns that produced a new kind of pottery called Sue ware. The kilns were built on a hillside and could reach temperatures in excess of 1000 C, resulting in highly durable, gray pottery. The largest production area was in Osaka, near the present-day cities of Sakai and Izumi, and many examples of Sue pottery have been found in the tombs here. Kofun from the fifth and sixth centuries are filled with Sue ware and far more iron than in earlier burial mounds.
By the end of the fifth century, gold had become the most desirable material for burial goods. Tombs from this era are often filled with gold-plated swords and horse tack, as well as jewelry and gold crowns and slippers. Even more than iron during the fourth and fifth centuries, gold conveyed power and authority, especially as iron became easier to produce. Very few people had the wealth to acquire gold; by investigating the tombs from this period, archaeologists have been able to get a sense of the social stratification of the time.
During the sixth century, the dimensions of kofun shrink, and their design changed from chambers sealed on the top to chambers with a horizontal passageway to the outside, which could be reopened to inter more remains. Although powerful clans still built massive earthworks, smaller tombs became far more common.
The Shura Sledges and Modern Scientific Preservation
Finding wooden objects in a kofun is rare; two of the most important surviving objects on display are wooden sledges (shura), which are thought to have been used to move massive stones during the construction of a kofun. The museum’s larger shura was carved from the trunk of a Japanese evergreen oak and is 8.8 meters long and weighs about three metric tons. Experts believe the holes in the sides were used for attaching ropes to pull the sledge over a path of wooden rollers. The two shura appear to have been preserved because they were submerged in mud. To prevent the wood from deteriorating after being removed from the mud, the moisture in the wood was gradually replaced with a polyethylene glycol compound. The treatment took 14 years to complete.
