The sintering of green bodies is measured in-situ with high reproducibility at Fraunhofer Center HTL and subsequently optimized. The result of sintering is strongly influenced by the furnace atmosphere for many materials. Suitable ThermoOptical Measurement Systems (TOM) are available at the HTL for most technically relevant furnace atmospheres and temperature ranges. In this way, sintering can be carried out in graphite-, molybdenum disilicide-, or tungsten-heated measurement furnaces. Inert gases, oxidizing or reducing gases - including 100% hydrogen - can be used as furnace atmospheres. Some TOM systems can be operated under vacuum or overpressure (up to 30 bar). The furnace atmosphere in gas-heated furnaces can also be accurately reproduced. Matching the furnace atmospheres between the production furnace and the TOM system used is extremely important because only then can the sintering conditions optimized by the TOM system be transferred to the production furnace. In addition, temperature matching of the affected furnaces is usually carried out using specially calibrated temperature measurement rings.