Raku-yaki is lead-glazed tea pottery made for tea ceremony which is fired relatively briefly and usually freely moulded by hand. It was initially produced only in the colours red (aka-raku) and black (kuro-raku), with white, amber and, rarely, green oribe raku bowls being later additions. Raku bowls feel very soft and warm, absorb a lot of moisture and gain patina and beauty over time. They are considered the finest bowls for tea ceremony, with red and black considered the best colours to complement the bright green matcha. The first raku bowl is said to have been made around 1579 by the brickmaker Chōjirô under the guidance of the great tea master Sen no Rikyû. After his death, Chōjirô was honoured by Prince Hideyoshi by bestowing the raku seal upon his successor, Jôkai. Since then, the Jôkai family has used the name Raku and, along with a few smaller potteries, still produces these exceptional tea accessories in Kyoto.
Black raku (kuro raku, 黒楽) requires a special rough clay containing sand and a high iron and manganese content from the Kamigawa River in Kyoto. In Japan, the special black quality of the bowl is considered the best colour to bring out the bright green of the matcha. The Raku family ensures to dig out and store enough clay for the three following generations. Several layers of glaze (kamogawa-ishi) are cut and applied with pressure, then covered with a transparent raku glaze. The 1,200-1,250°C firing temperature is relatively high, and the red-hot bowl is removed after only 8-10 minutes to cool. The result is a non-sintered, high-fired earthenware. Authentic kuro raku bowls have a small dent on the side where they are cut out.