The Elcometer 5100 Payne Permeability Cups (part numbers K0005100M201, K0005100M202 and K0005100M203) are anodised aluminium cups used to determine the permeability of films of paints, varnishes, plastics, cellophane and similar materials. A coating's resistance to water vapour passing through it governs whether it protects or breathes as intended, so measuring permeability informs decisions on protective coatings, packaging films and breathable finishes.

In use, the film to be tested is applied with a film applicator and suitable test chart, then sealed across a cup filled with water or a dry desiccant, with a gasket fitted to ensure a tight seal. The cup is weighed, left for a set time, then re-weighed. Water either evaporates from or is absorbed into the cup, and the change in mass relative to the film thickness gives the water vapour transmission rate, indicating the degree of permeability or permeance. The cups are designed for use with the Elcometer 8720 Compact Balance, which records the weight change.

Three cup sizes are offered: the 5100/1 with a 10 cm2 area and 15 cm3 volume, the 5100/2 with a 30 cm2 area and 50 cm3 volume, and the 5100/3 with a 30 cm2 area and 75 cm3 volume. The cups can be used in accordance with ASTM D1653, ASTM E96, ISO 7783-1 and ISO 7783-2. They are supplied by BAMR, South Africa's authorised Elcometer distributor.