Effect of Vessel Wettability on the Foamability of “Ideal” Surfactants and “Real-World” Beer Heads

The ability to tailor the foaming properties of a solution by controlling its chemical composition is highly desirable and has been the subject of extensive research driven by a range of applications. However, the control of foams by varying the wettability of the foaming vessel has been less widely reported. This work investigates the effect of the wettability of the side walls of vessels used for the in situ generation of foam by shaking aqueous solutions of three different types of model surfactant systems (nonionic, anionic, and cationic surfactants) along with four different beers (Guinness Original, Banks’s Bitter, Bass No. 1, and Harvest Pale). We found that hydrophilic vials increased the foamability only for the three model systems but increased foam stability for all foams except the model cationic system. We then compared stability of beer foams pro­duced by shaking and pouring and demonstrated weak qualitative agree­ment between both foam methods. We also showed how wettability of the glass controls bubble nucleation for beers and champagne and used this effect to control exactly where bubbles form using simple wettability patterns. Keywords: Foamability, Foam stability, Wettability, Contact angle, Beer head control, Hydrophobic–hydrophilic

Figure 5 is in color in this online article.