Mould materials are exposed to extreme thermal and mechanical loads during large scale steel castings. For some time chromite and zircon sands have been used but were not optimized. Despite the use of these moulding materials surface defects are generated, which cause expensive repair welding and frettling work. Therefore a systematic investigation was performed to study variations of moulding materials and additives to eluciate their effects in casting practice. In particular novel mould washes and base sands were tested in submerge tests and casting experiments with steel melts. The influence of different additives on the casting performence was successfully determined. It was shown that submerge tests of mould materials in steel melts can be used to obtain reproducable conditions akin to long scale steel castings.