use of this method and apparatus to mixing in rigid but partially filled containers such as bottles by performing the mixing in the primary storage container this method provides containment and eliminates labor intensive cleaning and sterilization of additional mixing tanks the gentle wave motion provides an intrinsically low shear environment and reduces damage due to foam as there is no invasive mixer the container can be u201c closed u201d so that no contaminants can be introduced from the environment nor are any hazardous materials released from the container the invention is useful in various industries especially for handling sterile and hazardous materials contained in sealed pre sterilized plastic bags a typical embodiment of the invention is shown in fig1 the plastic bag 4 contains the ingredients and liquid 20 to be mixed to ensure sufficient wave motion for mixing it is critical that the bag not be filled to full volume sufficient volume must be available in the bag to permit liquid motion and wave formation typically the bag must not be filled beyond 80 of its total volume with the liquid containing the ingredients to be mixed the exact limit will depend on the bag geometry employed the partially filled plastic bag 4 is placed in bag holder 6 that is in turn placed on the rocking platform 1 the bag holder is attached to the platform in a manner such that it does slip or fall off during motion the platform can rock or tilt in one axis about the pivot point 2 which is rigidly attached to.