The assembly of colloidal particles at a liquid/liquid interface is a useful technique for the formation of a large variety of structures. Recently, we created a new method which uses liquid/liquid interfaces to assemble recombinant silk proteins into thin-shelled microcapsules. These microcapsules are mechanically stable and well suited to applications such as enzyme therapy and artificial cells. In this paper the permeability properties of these microcapsules are investigated using a novel measurement technique. It is found that the microcapsules are polydisperse in their permeabilities, but for all measured microcapsules the permeability is in the range required to protect encapsulants from immunoglobulin proteins, while allowing small molecules to enter the capsule freely.