Why Soap Lathers

Soap Ingredients

Soap is a combination of a number of ingredients. All soaps contain acids, which are actually fats or oils added to a base, and alkali products such as lye or potash. The combination of oils or fats with alkali products creates soap lather, which suspends dirt by creating greater surface tension in water, trapping dirt for easy removal through rinsing. Lathering differs from brand to brand in soap, because how soap lathers depends on what sort of oil it contains. Ingredients such as salt, milk or even sugar also affect the lathering process, but the main factor for good lather is the oil or fat used.

Common Oils in Soap

Oils that are commonly used in soaps range from avocado to coconut. Bean oils such as soybean or peanut can also be included. Lard and tallow create a stable lather, but will not foam up as much as avocado, coconut and Castor oils. Ideally, any soap you use for personal skin care lathers in two ways. One, the soap will produce a foamy, fluffy lather, and secondly the lather will be stable enough to pick up dirt well. Most soaps use a combination of oils that produce both fluffy and stable lathers, or Castor oil, which produces both kinds of lather. The type of oil used influences not only what kind of lather is produced, but also whether the final product, the soap, will be hard or soft. Coconut, palm, lard and tallow will all produce a hard soap, whereas olive oil, almond oil and jojoba oil will produce soft soaps. Soaps that contain coconut oil or Shea butter not only produce hard bars of soap, but also moisturize and lather well, making them very high-quality soap ingredients.

How Water Influences Lather

Soap will lather less or perhaps not lather at all in hard water, which is water that contains dissolved minerals such as calcium and magnesium. The oils in the soap, which are acidic, react with the calcium and magnesium in the water, and this negatively affects the soap's lathering quality. Soft water does not contain a measurable amount of minerals and will produce a better lather. An automatic water softener can be installed on water supply pipes for home use. Automatic water softeners act to remove minerals from water and replace them with sodium, which does allow soap to lather.