Gourd with Hidasuki
Hidasuki is the name given to the red stripes, which are made by wrapping rice straw around the vessel before loading it in the kiln. The gases released when the straw burns include potassium, magnesium, sodium, and other elements. These react chemically with the clay, which is mostly silicon and aluminum with a little iron, and yield a glaze. The rice straw ash that remains is almost 100% pure silicon; because of the relative absence of impurities, it does not melt at temperatures normally attained in my kiln, so it helps to keep stacked pots from fusing together during the fire. In addition, the rice straw provides a bit of protection for the fragile greenware during the loading process.