Why does the rim take on a yellowish tint after undergoing the 'high-temperature firing' mentioned in the description?

While the body is a neat white, a pale yellowish tint appears along the rim of the dish.

Firing is the process of baking clay-formed objects at high temperatures inside a kiln to make them hard and finished. As the ceramic withstands the hot heat in the kiln, the glaze applied to the exterior melts and flows, settling more thinly on edges or thin rims than on flat surfaces. Through this thinner layer of glaze, the clay's inherent components react to the heat and flames, bringing a faint yellowish cast to the surface.

HORIE TOUKI's white porcelain dishes can also take on a yellowish tint around the rim during the process of being baked at high temperatures^[1][2]. Along with this, glaze pooling or tiny black spots may appear on the surface, but these are not defects; they are natural characteristics unique to ceramics that have undergone high-temperature firing^[3].