Airy lather usually is a result of inadequate soap type (i.e. using a non-shaving soap, or if the stuff was bought as shaving soap, the maker not knowing what constitutes a decent shaving soap). In this context, I must however assume that you are using a decent shaving soap, and that you have already experienced this soap to be decent. In that case I would sincerely suspect the scuttle, more specifically the use of (too) hot water to keep the lather warm. Heating up the lather will 'blow' up the bubbles, making the lather go airy much much quicker than when you keep it cool, or at least at a steady temperature. Try with cold, or lukewarm water in the scuttle, and see if that makes a difference...