In IS machines, between the shears and the blank mould the glass gob is in contact with the cold delivery system which induces considerable temperature gradients in the gob surface. Because of the strong dependence of the viscosity on temperature, this often causes problems such as hot cracks or an unfavourable glass distribution. In a current research project, temperature distributions in glass gobs are measured by means of pyrometers using different wavelengths. Finite element method calculations are used in order to reconstruct the internal temperature profiles from the measured data as well as to relate them to the influence of the delivery system. The temperature decrease at the surface of the gob can be explained as a function of heat loss by radiation and by contact with scoop, trough and deflector. There is also evidence that the heat transfer coefficient in the trough decreases as the gob travels through the trough.
