A simple realiable  device for measuring the permeability to moisture of paint, varnish and lacquer film.
It consists of a flanged cup made of "Duraluminium" to which a disc of material under test is clamped by means of an inner ring and screw cap. Various backing materials have been suggested for supporting the film under test. The ring and flange of these cups are accurately machined to give exposure to exactly 10cmq of film; larger cups can also be supplied to yield a greater area of 25 cmq.