The present invention relates to a device for producing a hardenable mass,preferably bone substitute and/or bone reinforcing material or bone cement orsimilar material. A mixing container (3) has a mixing space (4) in which atleast one powder and at least one liquid component (5, 6) are mixed to providethe hardenable mass (2). A piston means (7) is provided in the mixing space(4) of the mixing container (3). At least one means (8) which is rotatablerelative to the mixing container (3) cooperates with the piston means (7) for,in a retaining position (P1), retaining said piston means (7) relative to themixing container (3) and, by rotation to a release position (P2), releasingthe piston means (7) such that said piston means can move in a direction (U)towards at least one opening (49) through which said mass (2) can pass out ofthe mixing space (4). The rotatable means (8) is provided such that it in itsrelease position (P2) can follow the piston means (7) in the mixing space (4)in the direction (U) towards said opening (49).
