Appearance: The surface should smooth, not allowed air bubbles, stains and impurities, allowed light scrapes; edges should incised tidily, not allowed layered and cracks in the surface.

• 外观:表面应平整光滑,不允许有气泡、麻眼和杂质,允许有轻微擦伤,边缘应切割整齐,端面不得有分层和裂纹。