symmetry can be aided by the localized edge support and clamping conditions discussed above i e by developing such edge support and clamping conditions with non rotational symmetry fig4 shows another embodiment having two elastically mounted auxiliary pistons 8 which are also connected to a hydraulic actuating system in this case different pressures or variations in pressure can be established for the two auxiliary pistons to achieve particular aspherical surfaces of non rotational symmetry in the various embodiments at least one of the deformable molding plates 5 may be of toric development alternatively the rigid surface 5a may be of toric development further the molding cavity surfaces 5 6 may be so arranged with respect to each other that planes tangential to their respective center points from an angle with each other it will be understood that beyond the spaced array configuration of two auxiliary pistons 8 in fig4 it is possible to arrange one or more additional auxiliary pistons within one piston 2 and in this way to produce either particularly complex aspherical surfaces of non rotational symmetry or surfaces which cannot be obtained by variation of the other parameters another advantage of a plurality of auxiliary pistons in.