Foaming agent Foaming agent A foaming agent is a material that facilitates formation of foam such as a surfactant or a blowing agent. A surfactant, when present in small amounts, reduces surface tension of a liquid (reduces the work needed to create the foam) or increases its colloidal stability by inhibiting coalescence of bubbles. A blowing agent is a gas that forms the gaseous part of the foam. Sodium laureth sulfate, or sodium lauryl ether sulfate (SLES), is a detergent and surfactant found in many personal care products (soaps, shampoos, toothpastes, etc.). It is an inexpensive and effective foamer. Sodium lauryl sulfate
Liquid as a linear medium, so that sound propagates without dissipation and without mode coupling. In reality, any liquid shows some dispersion: with increasing frequency, "K" crosses over from the low-frequency, liquid-like limit formula_6 to the high-frequency, solid-like limit formula_7. In normal liquids, most of this cross over takes place at frequencies between GHz and THz, sometimes called hypersound. At sub-GHz frequencies, a normal liquid cannot sustain shear waves: the zero-frequency limit of the shear modulus is formula_8. This is sometimes seen as the defining property of a liquid. However, just as the bulk modulus "K", the shear modulus "G" is