TOM_mech is a ThermoOptical Measuring (TOM) device for the investigation of mechanical high-temperature properties of materials. By combining a large-volume MoSi2-heated furnace with a commercial mechanical testing rig, samples up to a length of 300 mm can be measured at precisely specified temperatures and atmospheres. A large test volume is important especially for highly heterogeneous materials such as refractory materials, coarse pottery and ceramic matrix composites. Multiple sample holders are used for efficient implementation of high-temperature measurement series. Deformations are measured directly in the hot zone of the furnace by an optical measurement system, so that, in contrast to conventional high-temperature test systems, falsification due to temperature gradients in the force transmission setup are excluded. Integrated microphones serve for acoustical crack detection. Variable measurement systems allow the examination of the mechanical behaviour under bending, compression, tensile and torsional loads up to a maximum of 1,750 °C. Using an integrated muffle and separate gas inlets to the heaters, measurements under non-oxide atmosphere are also possible. The resolution for uniaxial force measurement is 180 N, for torque 0.8 Nm and for strain (optical measurement) 1 µm, whereby mechanical strain transducers may also be used.