Vacuum physics applied to the transport of gases through cork

In this work we apply common vacuum technology approaches to study the permeation of gases trough cork. A mass spectrometer leak detector was used to directly measure the helium flow through the central area of small cork discs. The permeability for other gases and vapors was measured by the pressure rise technique. The flow of gases is modeled using the conductance concept applied to small channels between cork cells. Hence, flow is performed via many series and parallels of individual conductances. The calculated diameter for such channels, in a typical sample, is below 100 nm, well in accordance with the ultrastructure observations of cork. The flow rate for several gases shows a dependency on the permeant mass typical of molecular flow. However, the observed largest permeation rate for vapors is an indication that, in this case, transport is also performed by means other than the small channels.