<p>An autoclave oven assembly subjects a porous mineral-based product (5) to steam pressure, and consists of a mantle (1) surrounding a horizontal cylindrical chamber (2) heated by a steam generator (11). The novelty is that metal side curtains (6) separate lateral steam passages (8') from the remainder of the chamber (2). The lateral steam passages (8') receive steam from a blower, and the curtain (6) base incorporates jet-like drain holes (9) for superheated steam. The holes (9) are so dimensioned and distributed along the curtain (6) base, that there is uniform surrender of heat from both sides of the chamber (2) to the charge (5). The upper zone of the autoclave mantle (1) incorporates suction outlets (10) for the steam.</p>
