素 (plain) and 焼 (bake) combine as すやき, a jukujikun reading. 素 is read with its Kun'yomi す, not On'yomi そ. 焼は Kun'yomi やき, not け. It denotes pottery that has been fired once but not yet glazed, often called bisque firing or unglazed pottery.

素も焼も訓読みで「すやき」と読み、熟字訓の一つです。素の音読み「そ」ではないことに注意。釉薬をかけずに焼いた陶磁器、またはその工程を指します。