The surface composition of the tin side of float glass has been investigated by XPS and found to contain a large quantity of tin in the near surface region resulting in an increase in refractive index and viscosity. Transmission Mossbauer spectroscopy was used to examine tinted glass and the oxidation of Sn2+ to Sn4+ was found to take place on heat treatment as in clear glass. Conversion electron Mossbauer spectroscopy was applied to both clear and tinted glasses and showed that tinted glass had a greater proportion of Sn4+ and that both clear and tinted glass showed faster conversion of Sn2+ to Sn4+ in the near surface region on heat tratment. Bloom was only seen on glasses for which this conversation occurred at a temperature where the surface viscosity was sufficiently low for wrinkling to occur.
