The invention provides a method of operating a batch mixer for producing first and second numbers of mixtures from first and second numbers of batches of materials to be mixed in the batch mixer, the batch mixer comprising a mixing chamber, a mixing element disposed within the mixing chamber, the mixing element and the mixing chamber being configured for providing an identical flow of the materials to be mixed within the mixing chamber and around the mixing element regardless of in which of the first and second opposite directions the mixing element is rotated, and a motor assembly coupled to the mixing element for rotating the mixing element for mixing the first and second numbers of batches of materials to be mixed for producing the first and second numbers of mixtures. The method comprises the steps of energizing said motor assembly for rotating said mixing element in said first direction, for each one of the first number of batches of the materials to be mixed: loading the one of the first number of batches of materials to be mixed into the mixing chamber, mixing the one of the first number of batches of materials for producing one of the first number of mixtures, and removing the one of the first number of mixtures from the mixing chamber, energizing the motor assembly for rotating the mixing element in the second direction, and for each one of the second number of batches of the materials to be mixed loading the one of the second number of batches of materials to be mixed into the mixing chamber, mixing the one of the second number of batches of materials for producing one of the second number of mixtures, and removing the one of the second number of mixtures from the mixing chamber.
