Abstract: This invention concerns the heating of a liquid, such as milk, by steam infusion and involves the formation of the liquid into a descending curtain that is initially generally frusto-conical in configuration and later is generally cylindrical as it passes through an atmosphere of steam. The curtain is of relatively small diameter at its upper end and continually increases its diameter as it moves downwardly, thus, not only causing the thickness of the film to progressively decrease but also causing the surface area of the film to be greatly enlarged.