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 said batch mixer, said batch mixer comprising: a mixing chamber, a mixing element disposed within said mixing chamber, said mixing element and said mixing chamber being configured for providing an identical flow of said materials to be mixed within said mixing chamber and around said mixing element regardless of in which of the first and second opposite directions said mixing element is rotated, said mixing element comprising at least two mixing paddles for mixing said materials to be mixed, said mixing paddles being arranged in said mixing element such that rotation of said mixing element, in either of said first direction or said second direction, causes said materials to be mixed to flow, at the same rate regardless of the direction of rotation, towards the centre of said mixing chamber or alternatively towards the opposite ends (26, 28) of said mixing chamber, a motor assembly (22, 24) coupled to said mixing element for rotating said mixing element for mixing said first and second numbers of batches of materials to be mixed for producing said first and second numbers of mixtures, the method comprising the steps of: - energizing said motor assembly (22, 24) for rotating said mixing element in said first direction, - for each one of said first number of batches of said materials to be mixed: - loading said one of said first number of batches of materials to be mixed into said mixing chamber, - mixing said one of said first number of batches of materials for producing one of said first number of mixtures, and - removing said one of said first number of mixtures from said mixing chamber, - energizing said motor assembly (22, 24) for rotating said mixing element in said second direction, and - for each one of said second number of batches of said materials to be mixed: - loading said one of said second number of batches of materials to be mixed into said mixing chamber, - mixing said one of said second number of batches of materials for producing one of said second number of mixtures, and - removing said one of said second number of mixtures from said mixing chamber. characterized in that each of said mixing paddles comprising a closed elongated prism having a first face orthogonal to the axis of rotation of said mixing element and second and third faces (80, 82) forming first and second identical angles to said first face. a mixing chamber, a mixing element disposed within said mixing chamber, said mixing element and said mixing chamber being configured for providing an identical flow of said materials to be mixed within said mixing chamber and around said mixing element regardless of in which of the first and second opposite directions said mixing element is rotated, said mixing element comprising at least two mixing paddles for mixing said materials to be mixed, said mixing paddles being arranged in said mixing element such that rotation of said mixing element, in either of said first direction or said second direction, causes said materials to be mixed to flow, at the same rate regardless of the direction of rotation, towards the centre of said mixing chamber or alternatively towards the opposite ends (26, 28) of said mixing chamber, a motor assembly (22, 24) coupled to said mixing element for rotating said mixing element for mixing said first and second numbers of batches of materials to be mixed for producing said first and second numbers of mixtures, - energizing said motor assembly (22, 24) for rotating said mixing element in said first direction, - for each one of said first number of batches of said materials to be mixed: - loading said one of said first number of batches of materials to be mixed into said mixing chamber, - mixing said one of said first number of batches of materials for producing one of said first number of mixtures, and - removing said one of said first number of mixtures from said mixing chamber, - loading said one of said first number of batches of materials to be mixed into said mixing chamber, - mixing said one of said first number of batches of materials for producing one of said first number of mixtures, and - removing said one of said first number of mixtures from said mixing chamber, - energizing said motor assembly (22, 24) for rotating said mixing element in said second direction, and - for each one of said second number of batches of said materials to be mixed: - loading said one of said second number of batches of materials to be mixed into said mixing chamber, - mixing said one of said second number of batches of materials for producing one of said second number of mixtures, and - removing said one of said second number of mixtures from said mixing chamber. characterized in that each of said mixing paddles comprising a closed elongated prism having a first face orthogonal to the axis of rotation of said mixing element and second and third faces (80, 82) forming first and second identical angles to said first face. - loading said one of said second number of batches of materials to be mixed into said mixing chamber, - mixing said one of said second number of batches of materials for producing one of said second number of mixtures, and - removing said one of said second number of mixtures from said mixing chamber. characterized in that each of said mixing paddles comprising a closed elongated prism having a first face orthogonal to the axis of rotation of said mixing element and second and third faces (80, 82) forming first and second identical angles to said first face.