Abstract: An apparatus of coating a filter substrate comprising a plurality of channels and an apparatus is disclosed. The apparatus comprises: (i) a containment means for receiving a pre-determined amount of the liquid; and (ii) a liquid dosing head arranged to dispense the pre-determined amount of the liquid into the containment means over an upper end of the filter substrate. The containment means is locatable at an upper end of the filter substrate; and the liquid dosing head comprises a plurality of apertures for dispensing the liquid onto the upper end of the filter substrate.