On the origin of the tin hump in several float glasses

It has long been known that some commercial float glasses display an anomalous tin hump several micrometers below the glass surface at the tin bath side. The literature offers different explanations. After precise measurement of the in-depth profiles of all relevant species and also the in-depth profile of the Sn2+/Sn4+ ratio, a diffusion-reaction model was developed. Its main assumption is that when the oxidized glass melt enters the strongly reducing float chamber, a drastic and rapid change in the oxidation state occurs in the glass melt near its surface. The anomalous tin hump follows then as an interaction between the ongoing diffusion processes and redox reactions, at a position identical with that of the maximum in the Sn4+ profile.