Method of coating a substrate with a washcoat

1. A method of coating a substrate with a washcoat, wherein the method comprises the steps of:

engaging the substrate with a headset of a substrate coating apparatus so as to locate an upper surface of the substrate below a washcoat showerhead of the substrate coating apparatus;

discharging a washcoat out of the washcoat showerhead towards the upper surface of the substrate;

drawing the washcoat through the substrate by applying a suction force to a lower surface of the substrate,

wherein the step of engaging the substrate with the headset comprises engaging a headset seal of the headset with the substrate, the headset seal comprising a perimetral portion extending around the headset and a cantilevered portion extending down from the perimetral portion which engages against a sidewall of the substrate.

2. The method of claim 1 , wherein the cantilevered portion is arc-shaped.

3. The method of claim 1 , wherein the upper surface of the substrate comprises a shaping which extends to the sidewall of the substrate, thereby defining a gap in the sidewall, wherein the cantilevered portion bridges over the gap to hinder leakage of the washcoat out of the gap and down the sidewall of the substrate.

4. The method of claim 3 , wherein the shaping is a groove or cut-out.

5. The method of claim 1 , wherein on engaging the substrate with the headset, the cantilevered portion of the headset seal flexes in a substantially radial direction.

6. The method of claim 1 , wherein the cantilevered portion extends at an angle of between 0° and 15° with respect to a plane perpendicular to the perimetral portion.

7. The method of claim 1 , wherein the cantilevered portion extends at an angle of between 0° and 10° with respect to a plane perpendicular to the perimetral portion.

8. The method of claim 1 , wherein the cantilevered portion extends at an angle of about 3° with respect to a plane perpendicular to the perimetral portion.