Why doesnt old soap make suds effectively?

When a bar of soap gets used a lot and gets smaller, it seems to struggle to form suds properly. Is something other than just a smaller surface area going on? Eva Higginbotham has been scubbing up to answer this question with the help of Phillip Broadwith, Business Editor at Chemistry World, and Paul Dauenhauer from the University of Minnesota... Like this podcast? Please help us by supporting the Naked Scientists