Abstract: A method and apparatus for proportionally stretching a skin in multiple directions from the center of the skin. The degree of stretching is proportional to the distance of the periphery of the skin from its center. The skin is clamped at its periphery to multiple perforated pivotable plates which stretch the skin upon contact with a cover member. The cover member hermetically seals the skins whereupon a subatmospheric pressure is applied thereto at a temperature below 75.degree. C.

Abstract: The present invention relates to an apparatus for drying under vacuum flat articles of porous material which apparatus comprises a support surface for supporting at least one article to be dried, a heating means disposed on the side of the support surface opposite to the side supporting the flat articles, at least one cover means serving to enclose at least one article to be dried, which is spread on the corresponding portion of the support surface, in a hermetically-sealed space, and means enabling the connection of the hermetically-sealed space to a vacuum creating device. The cover means employed comprises a flexible but non-extensible, fluid tight diaphragm which is provided on the side facing the support surface with a cushion layer of porous material and on its periphery with a fluid-tight seal for coaction with the support surface to provide the hermetically-sealed space.