Permeability Cups (also known as Perm Cups or Payne Cups) are used to determine the permeability of films to water vapor and other liquids. Materials tested include paint, varnish, thin plastic films, and other types of sheets thin enough to be tightly sealed across the face of the cup. Permeability is expressed as the weight of vaporous material that passes through a specified area and thickness of free film within a specified time interval under controlled conditions
Each Perm Cup consists of three basic parts, each machined from the highest grade anodized aluminum. The top surface of the cup, as well as both surfaces of the clamp ring, are smoothly finished to provide a tight seal against the product under test. Two gaskets, with the same dimensions as the clamp ring except for thickness, are provided for use with rough or uneven materials to ensure complete sealing. Extending upward from the face of the cup are two stainless steel pins, which closely engage the clamp ring and any gaskets used, preventing movement of the test material as the cap is tightened against the cup. The cap design allows for the use of longer pins than in earlier models, accommodating thicker sample and gasket combinations
Standards
ISO 7783:2018 — Paints and varnishes — Determination of water-vapour transmission properties — Cup method
ASTM D1653-13(2021) — Standard Test Methods for Water Vapor Transmission of Organic Coating Films
