The evolution of radial cracks generated by Vickers indentation on tin side of float glass is analyzed when heat treated at 620 degrees C under various atmospheres and results are compared with a previous similar study performed on the air side of the same glass. Results evidence that the presence and the oxidation state of tin ions has a strong influence on crack morphological changes. If the oxidation state of tin remains quasi unchanged during the heat treatment, the mechanism responsible of the crack evolution is the spheroidization and there is no strong difference between the crack morphological changes observed on the air and tin side in this case. For oxidative atmospheres, contrary to what is observed on the air side, no crack spheroidization occurs. The cracks stay quasi unchanged for dry air or close for humid air. Increase of the viscosity at the top surface due to Sn oxidation is proposed to explain this spheroidization impediment. It is also shown that in these two cases, there is an efficient blunting and healing of the cracks, as 4-point bending tests indicate a significant sample strengthening with thermal treatment.