Liquid silicone rubber (LSR) has good chemical and physical properties, in particular, it is biocompatible and weather-proof and it can be used between -50°C and 200°C. However, it is more expensive than other elastomers. For this reason, the density should be reduced to get lower the price for parts. By producing LSR foams, the density can be reduced to below 1 g/cm³. Besides, the haptics of the components and the thermal insulation properties are improved. LSR is used in liquid injection molding. Due to this processing method, the blowing agent has to expand inside the hot mold (150°C up to 200°C) to create the foam structure. Possible blowing agents are physical blowing agents such as thermoplastic expandable microspheres or water. The foam structure depends on the different blowing agents and their amount as well as on the processing parameters. The cell structure is very homogeneous with microspheres as blowing agent, but with water the structure becomes inhomogeneous. To improve the foam structure it is possible to use additives such as pyrogenic silica. The foam structure and the blowing agents influence the mechanical properties like the shore hardness and the tensile strength.