Sudsing

Sudsing refers to the creation of foam, or lather, when a liquid containing surface-active agents is agitated. Surfactants reduce surface tension and arrange at air-liquid interfaces to form a film around gas bubbles. If the film is sufficiently stable, many bubbles coalesce into foam. The height and persistence of suds depend on the liquid, surfactant concentration, temperature, and the level of agitation.

In household products such as soaps, shampoos, and detergents, suds are common. The presence of suds can aid perceived cleaning, but the amount of foam does not directly indicate cleaning power. Some applications favor low-suds formulations to prevent overflow in automatic washing machines, while manual cleaning may tolerate or even prefer more foam.

Factors influencing sudsing include the type and concentration of surfactants, water hardness, temperature, pH, and agitation. Anionic surfactants tend to generate more foam than nonionic ones, and minerals in hard water can interact with soaps to form scum that reduces visible suds. The stability of foam is also affected by additives such as polymers and electrolytes.

In industrial settings, excessive sudsing can cause process overflow and sensor interference. Anti-foaming or defoaming agents, often silicone-based or hydrocarbon blends, are used to control foam when high levels are undesirable. Sudsing is sometimes evaluated with standardized foam tests, but results vary with formulation and operating conditions.