Thermal analysis is a widespread investigation method used to interpret different phase transformation phenomena in the metal / mold domain at production of cast components. The focus in this work is on cast iron and sand aggregates used for mold and core production. Thermal instabilities and various thermal resistances are studied with the help of numerical casting simulation methods. Two major parameters influencing the temperature measurements, the stability of the thermal domain and the setting up of the thermocouples are discussed as the major contribution for uncertainties when the registered cooling conditions are interpreted with respect to phase transformation, property, and defect formation.