Siltas produces resin coated sand for shell moulding processes.

The Inventor of this process is Johannes Croning (Also patented in 1944)

The point was to improve the dimensional accuracy of series castings that were manufactured with natural sand (clay bonded) in order to save cleaning and finishing costs.

Cores used to be made with green and oil-bonded sands, and thus always tended to undergo deformation during the drying process. These cores used to be made in the shape of solid cores. Because of the low strength of the binders they were always required the reinforcement with "core iron" to ensure the stability during pouroff.

The shell moulding process eliminated these disadvantages due to high strength of the synthetic resin binders resulted in reinforcement of the cores was not necessary anymore.

By applying this new process, it is possible to produce hollow cores and thin masks (called shells) rapidly and with a precise dimensional accuracy instead of solid cores.