The disclosure relates to a substrate coating apparatus that comprises a source of a washcoat; a washcoat showerhead for discharging the washcoat towards an upper surface of a substrate; a conduit fluidly connecting the source of the washcoat to the washcoat showerhead for supplying washcoat to the washcoat showerhead; a headset for engaging the substrate to locate the upper surface of the substrate below the washcoat showerhead; and a vacuum generator for drawing the washcoat discharged from the washcoat showerhead through the substrate. The headset comprises a partition comprising a plurality of holes, the partition being located in between the washcoat showerhead and the upper surface of the substrate when the substrate is engaged in the headset so as to maintain a first gap between a lower face of the partition and the upper surface of the substrate.