This talk addresses the impact of tempering processes on the emissivity of LowE glass.

It introduces how the online monitoring by eddy current sensors can be used to monitor the change in emissivity. It suggests four strategies how the online emissivity monitoring can be used for improving the tempering performance and homogeneity and also to maximize the emissivity improvement as value add for furnace operators.

This paper presents the current status of measurement series conducted at different tempering sites on various types of LowE glass. The measurements have been made on the glass before and after tempering. The obtained data shows the emissivity improvement up to factor 2 and effects on homogeneity depending on the tempering recipe. It also shows significant worsening of the emissivity by using of wrong tempering settings causing too low convection during the heating causing significant glass bending leading to the well-known white marks in the middle of the glass. The study depicts such negative effects on the coatings and its emissivity properties measured by eddy current systems, so called EddyCus, which is an inductive method for contact or non-contact real-time emissivity assessment. Comparison to thermographic images are shown and discussed. Finally, the status of measurement and analysis are summarized and the potentials of a commercial use of these phenomena is discussed.