“…Although the majority of studies deals with single surfactant systems (see [1,2] for an extensive overview), foams stabilized by protein-surfactant mixtures [4][5][6][7], polymer-surfactant mixtures [8,9], alcohol-surfactant mixtures [10][11][12], solid particles [13][14][15][16][17] and liquid crystals [18][19][20] have also been investigated. However, there exists a lack of experimental data and thus a lack of knowledge on the foaming properties of surfactant-surfactant mixtures [21][22][23][24][25][26][27] although studying surfactant mixtures is indispensable in order to understand and to optimize technical products and processes where foam films and foams are involved.…”