Water-vapour penetration was measured on pouch, flat, wedge, and square liner bags fabricated from Reynold's Metal A-51, 300 M.S.A.T. "Cellophane" coated 40 lb. per ream with a flexible wax composition, 55 lb. laminated bleached glassine, and 300 M.S.A.T. Cellophane. The bags were closed, where the material permitted, by heat-, glue-, and pressure-sealing, and by folding with or without tin-tie closures.When Reynold's Metal A-51 or waxed Cellophane was used, excellent water-vapour resistance could be achieved with any of the bag types investigated, and a folded closure was as efficient as a heat-seal. With all materials except 300 M.S.A.T. Cellophane, bags made with glue were almost as good as those with heat-sealed construction. Unwaxed Cellophane or glassine provided more protection when the simpler forms of bags (pouch) were used. With unwaxed Cellophane, heat-sealing appeared to make a better liner than the use of glue, and a heat- or glue-sealed closure was superior to a double fold.
Heat seal processing by using various seal bar shape
