Take two ceramic tile again, glair faces glaze, or the reverse side is stuck to the reverse side neat, see ceramic tile whether have protruding sunken or phenomenon of the beat on cave in.

• 再拿两片瓷砖，釉面对釉面，或背面对背面贴齐，看瓷砖是否有凸凹或下陷上鼓现象。