Garnet commutator paper is non-conductive and is used for pre-shaping new copper and carbon brushes and for cleaning and burnishing commutator surfaces. With the new brushes in place, the commutator is rotated by hand until the brushes have taken on the radius of the commutator. - To pre-shape brushes, commutator paper of sufficient width to contact all brushes is secured, abrasive side out, to the full commutator circumference with masking tape.