There are many different types of pottery produced in Japan. Some of the finest varieties are made in the Western provinces, in areas such as Aki and Kyushu . The potters in these districts learned some of their skills from China, but many of the finest pottery techniques were invented uniquely in Japan
The most highly-regarded types of pottery, such as Suo-yaki and Hagi-yaki, are made from very fine-grained clays, which makes the pottery very smooth and delicate. To make sure that the clay is very fine, the potters may spend several days beating and kneading it to remove even the tiniest lumps or bits of sand. Although this is very hard work, the pottery that is produced by this technique is a much higher quality, and can be sold for a better price.
Apart from the quality of the clay, the most important point in making pottery is the baking process. The temperature of the ovens, the length of time that the pottery is bakes, and the speed of cooling the finished dishes all have an effect on the quality. These techniques are kept a secret within each guild of potters, and there are serious penalties for anyone who gives away the technology secrets. Most other crafts guilds have similar secret techniques that are passed down from generation to generation. The custom of keeping crafts techniques a secret within the guild helps the craftsmen of Edo maintain control over their markets, and keep prices relatively high.