A method of veneering curved work and forming laminated shapes which has supplanted the traditional sandbag technique, except for occasional work, is the rubber envelope which can take the place of the vacuum-bag press if necessary. Some form of vacuum extraction is
required, either a suitable vacuum pump, the intake side of a standard compressor, or the slip side of a blower motor. The household vacuum-cleaner is not suitable as a vacuum of 26 in (660 mm) of mercury must be induced. The envelopes are procurable from 4 ft (1.22 m) by 3 ft (0.91m) up to 12 ft (3.65 m) by 5 ft (1.52 m). The work to be veneered is placed on a suitable flat baseboard or support with loose flaring pieces either side to even out the pull on the rubber, and the whole assembly placed in the envelope, the open end of which is sealed with cramped/clamped battens. It is advisable to run crossed shallow grooves in the baseboard and flaring pieces with vertical holes at the intersections to allow the air to be withdrawn evenly. The usual precautions must be taken, i.e. formers, forms, etc. must be waxed to prevent adhesion or the veneers covered with waxed paper, with the veneers stapled through the waste to prevent displacement. Figures 295:1 and 295:2 show an enlarged diagram of a section of the assembly. The envelope can be used for flat-work, curved work and compound shapes with equal success, but the bag must be smoothed out and the shapes under held down as the air is withdrawn, to prevent the rubber drawing under the veneers.
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