Susceptibility to Mould Growth of Wad Materials Used in Glass Jar and Bottle Closures

SUMMARY: The relatively high mould‐resisting qualities of both wood pulp and felt board as compared with composition cork are not due to the presence of fungistatic substances. Wood pulp board withstands mould attack because of its comparatively inert nature. The apparent fungistatic property of felt is due mainly to the fact that a high humidity is necessary for it to support growth; when used in bottle closures the humidity at the interface between cap and wad is normally below that required for mould development on this material. Under conditions where mould could occur, growth at the interface seems to be limited by mechanical restriction.