Surface rheology
The surface shear viscosity of the air–liquid interface has
been measured using a CIR-100 Interfacial Rheometer
(Camtel Ltd., Royston, UK). All four solutions were tested
with an amplitude sweep, with the instrument in normalised
resonance mode, using a platinum/iridium de No+uy
ring, diameter 13mm oscillating at 3Hz at 25 1C.