Why is there a gap or wobbling between the bowls when stacking them neatly?

Looking first at the margin of error, product sizes may differ by ±1cm depending on the measurement method^[1]. HASAMI PORCELAIN crafts all its products from natural raw materials^[2]. Generally, when clay and minerals are blended and fired in a high-temperature kiln, moisture evaporates, causing the raw materials to shrink unevenly. Going through such ceramic firing processes causes each piece to differ slightly in size and shape, even among bowls of the same specification^[3].

When subtle, barely noticeable deformations occur along the rounded rim, gaps may form or wobbling may occur when stacking bowls, even if they have the same diameter^[4]. Even if they do not interlock completely and firmly, there is no problem with stacking them neatly upward for storage, so when stacking tableware, simply center each piece and place it straight. Depending on the natural properties of the raw materials, the surface coloration and tactile texture also appear uniquely on each piece^[5].

hmmm, rather than fitting seamlessly like machine-pressed industrial products, it is closer to the natural relaxed tolerance unique to ceramics that have set their individual shapes within flames.