Abstract: A demoulding composition, to be used for the production of parts of hydraulic-setting material, includes at least one oil and at least one calcium salt, calcium borates and calcium salts of fatty acids being excluded from the at least one calcium salt. A process for the preparation of a part moulded in hydraulic-setting material, includes coating sides of an appropriate mould with the demoulding composition; introducing a freshly-prepared hydraulic-setting composition; and removing the part from the mould after hardening and optional curing of the composition.