"Biscuit" [bisque porcelain] means fired twice, the first time at 980C/1,800F and then 1400C/2,550F which is the highest possible temperature for a ceramic and thus gives porcelain its unique qualities: fineness, whiteness, hardness, translucency and sonority. The first firing, known as the "degourdi" firing, will make the pieces porous and allow the glaze to set. As for the "biscuit" pieces, they are not glazed before the second firing, which allows them to keep their matte appearance as here thisLegendevase. It's usually said that bisque porcelain is more fragile, but it's absolutely wrong!!