The present disclosure provides a method of stiffening an outer layer of a wet extrudate, where the extrudate has a honeycomb cellular structure. The method includes extruding the extrudate through an extrusion apparatus and directing a substantially uniform flow of fluid onto the outer layer of the extrudate. The method also includes increasing the temperature of a binder material of the extrudate to its gelation point and stiffening at least the outer layer of the extrudate.