Rugged yet Warm: The Traditional Clay Nurtured by an Ancient Lake

The sculptural strength of Shigaraki ware and its texture, which feels as warm as human skin, are deeply rooted in the properties of its raw clay. Its home was the bottom of the "Paleo-Biwa Lake," the precursor to Lake Biwa, a massive lake that existed in the Shigaraki area about 4 million years ago. Over eons, sediment and the remains of plants and animals accumulated, forming an ideal clay layer for pottery known as the "Kobiwako Sōgun" (Paleo-Biwa Lake Group). It is this geological blessing that truly sets Shigaraki ware apart from ceramics from other regions.

Artisans expertly blend different types of clay extracted from this Paleo-Biwa Lake Group according to what they are creating. Two main types of clay are central to this process. The first is "kibushi nendo" (wood-fragment clay). This is an extremely fine-particle clay rich in fossilized plant matter, giving it strong stickiness, or high plasticity (the ability to be shaped without breaking). This clay facilitates smooth forming on the potter's wheel.

The other is "gairome nendo" (frog's-eye clay). This clay contains coarse, sand-like particles such as quartz and feldspar, and is characterized by its high fire resistance. Because it resists deforming even at high temperatures, it provides the structural strength that forms the backbone of the piece. It is especially indispensable for "ōmono-zukuri" (the making of large pieces), such as the large jars and ceramic bathtubs for which Shigaraki ware is famous. The combination of the supple kibushi clay, which aids in shaping, and the robust gairome clay, which supports the structure, is what has made Shigaraki ware's uniquely large and warm forms possible.

The influence of this unique clay extends beyond just how easy it is to shape; it encapsulates the very beauty of Shigaraki ware. Iron in the clay reacts chemically with the kiln's flames, developing a reddish-brown coloration known as "hiiro" (fire color). Furthermore, the feldspar grains in the gairome clay melt during the high-temperature firing process and appear on the vessel's surface as white specks. This effect, called "ishihaze" (stone bursts), is a hallmark of Shigaraki ware, which uses unrefined, coarse clay, and it creates a "scenery" that speaks to the raw power of the earth. What’s fascinating is that these beautiful decorations aren't painted on by an artisan's brush. Instead, they are a rustic beauty that emerges naturally when the material itself—the clay—meets the flames. It is as if the ancient memories of the lake, left behind in the earth, are brought to the surface of the vessel by the fire.