Abstract: An apparatus for forming composite articles which include the stretchable or pre-shaped membrane adapted to be placed on a mold in a ridged framework carrying an outer seal. An inner seal is attached to the membrane and located between the membrane and the inner side of the rigid framework defining a vacuum cavity. The membrane is attached to the seal at the lower most point thereof. The seals are substantially square in section and have cut-out sections to enhance resilience. The seals have a outwardly directed downwardly extended curtain portion to form a initial loose seal with a mold base.