An arare teapot is a style of Japanese teapot made out of cast iron and decorated with a pattern of evenly spaced bumps, known as arare. Most arare teapots have a distinctive disk-like shape. The pattern of bumps is also known as a hobnail design, and so these teapots may also be called "hobnail teapots. The bumps may be large or small, but are always evenly spaced and rounded.
The bumps on these teapots are usually located on the top side of the disk shaped teapot, and ends at ridge on the widest part of the disk-shaped teapot. Traditionally, the number of bumps in the first row is equivalent to that of the last row. A variant of this design is often called a partial hobnail arare, in which the top side of the teapot is not completely covered in bumps. In partial hobnail teapots, the design of bumps may form the shape of a triangle, or other evenly sided shape.
The arare design is most common to teapots made in Morioka, the capital city of the Iwate perfecture of Japan. Morioka has a long history of ironware production, and is considered by some to be the origin of this teapot design. These teapots are also made in the nearby Yamagata prefecture, as well as in China. Reportedly, one family owned business has been making teapots in this style according to traditional methods for over 90 years.
These teapots are a specific style of teapot belonging to a larger group called tetsubin teapots. Generally speaking, a tetsubin teapot is a Japanese style cast-iron teapot.
Traditional tetsubin teapots are made by sand casting. This process involves making a mold out of clay and sand and pouring in the molten iron. In the case of an arare teapot, the design is typically a feature of the original mold, rather than being added on later. Once the iron has cooled, the inner and outer sand or clay molds are broken to reveal the teapot. The surface of the teapot is sandblasted to smooth it, and an enamel coating is typically applied to the inside of the pot. At this point, any color or superficial design may be added, and the teapot is polished by hand.
Arare teapots and other decorative styles of tetsubin teapots are known for doing double duty. That is, they can be used to heat water directly on the stove, and are also aesthetically pleasing enough to be used for serving tea. Unlike with other metal teapots, the enamel lining of an arare teapot prevents the water from taking on a metallic taste. This is also the case with ceramic teapots, however these cannot be placed directly on the stove for heating water, and are only used for serving tea. In addition, the caste-iron construction of the teapot keeps tea water hotter than teapots made of ceramic, or other thinner metals.