Thermal conductivity is defined as the capability of a solid body, a liquid, or a gas to transport thermal energy. The speed at which thermal energy is transferred from one particle to another during heat-up of the material determines the conductivity. The (specific) thermal conductivity measured in Watt per Kelvin and meters is a temperature-dependent material constant.
Using the example of clay-bonded molding materials, table 1 illustrates the influence of changes in composition as well as packing density and temperature on thermal conductivity. Thermal conductivity is based on contact that the individual quartz grains form among each other. The bridging bonds increase the transport of heat, while at the same time the pore volume implements an insulating effect. Consequently, with increasing packing density the thermal conductivity of a material is increased since the contact surfaces are increased and the pore volume is minimized. An increase in water content causes increase in thermal conductivity; an increase in binder content increasesthe thermal bridges and thus the transport of heat. However, compared to water content these effects are less distinct.