Abstract: A unitary vacuum bag for forming of a fiber reinforced composite article, made of a fabric mesh reinforced curable elastomer, having a smooth surface on both sides. The bag is constructed upon the surface of the article which is to be reproduced and upon a planar flange extension of the mold for said article. A rigid vacuum chamber assembly consisting of a planar fiber reinforced composite or equivalent sheet is sealed on the outer periphery to the mold flange extension and on the inner periphery to the top surface of the bag by rubber seals which are attached to the vacuum chamber assembly under surface. A vacuum port through the vacuum chamber assembly between the rubber seals allows vacuum to be applied to the chamber causing it to be pressed by atmospheric pressure to the mold flange extension and bag periphery thus sealing the bag to the mold periphery and simultaneously providing a continuous vacuum source around the entire periphery of the bag.