The IR absorbance spectra of investigated glazes are illustrated in Fig. 6. All the spectra showed five characteristic peaks located at 1634 cm, 1401 cm, 1048 cm, 781 cm and 461 cm, respectively. The absorption band at 1634 cm was close to the position of H2O bending vibrations. The smaller intensity bands at 1401cm and 781 cm, could be assigned to the (PO4)3 asymmetric stretches of P–O–P bond. The absorption band at 1048 cm was assigned to the stretching vibration of Si–O, which indicated that the structure of the tested glazes was dominated by the so-called Q3 group (where Q is the number of bridging oxygen) [18,19]. The band at 461cm could be linked with the bending vibrations of two types of bridge bonds Si–O–Si and Si–O–Al [19].