A method and apparatus for impregnating a porous substrate with foam, the method comprising transporting the porous substrate through a nip region defined by a rotating foraminous drum and a foam discharge head, the foam discharge head comprising one or more discharge openings, supplying foam to the discharge head with pressure sufficient to discharge foam through the discharge openings to impregnate the porous substrate, and urging the foam discharge head and the foraminous drum toward each other to compress the porous substrate as it passes the discharge openings. The foam discharge head is mounted to a hinged plate to enable the urging of the discharge head toward the foraminous drum.