a new coated fibrous substrate is produced by applying a coating containing swelled super absorbent particles having a minimum dimension of at least 5 microns to obtain the desired porosity and roughness in the finished coating , applying the coating to the substrate at least partially setting the coating thereafter driving at least the majority of the carrier absorbed by the super absorbent particles from the particles to leave macro - voids in the coating and produce a coated surface having a roughness in the macro as opposed to the micro range .