This paper describes an investigation into premelting at the ice-glass interface. Using ellipsometry to monitor the thickness of the ice-glass interface, we show that no intrinsic premelting occurs at the interface between ice and smooth clean glass. However, premelting is observed at interfaces with roughened glass surfaces and with the introduction of surface impurities. Roughened glass which was made hydrophobic showed no premelting. The implications for theories of premelting are discussed.