Distinction among various silicate glasses with different boron bond structure is an important practical issue in the glass making industry. To this end, it has been suggested that microwave dielectric property characterization may be a useful tool to distinguish among these glasses since in the past this technique has shown the potential for characterizing different types of materials via their dielectric properties. Therefore, an existing 2-port transmission line measurement technique, using an HP8510B network analyzer, is used to measure the dielectric properties of four different types of glass specimens. These electrical properties are measured over a wide band of microwave frequencies covering X- and Ku-band (8.2 GHz-18 GHz). The results indicate that each glass specimen with its own specific chemistry (different boron chemistry) has distinct dielectric properties as function of frequency. It is also shown that these specimens can be easily distinguished from one another when inspected by an open-ended rectangular waveguide aperture probe for on-line, real-time and non-eontact testing of thin glass sheets.