To superfat soap is to leave unsaponified oils in the final bars for the mildest soap. Unsaponified oils do not form compounds with the other soapmaking components but, instead, remain in their original form in the bar as emollient ingredients.

The percentage of sodium hydroxide in a soap formula is carefully calculated according to the degree of saponification desired. (Remember, saponification is the process whereby the oil molecules and sodium hydroxides molecules mix to form the new substance — soap.) When enough sodium hydroxide is used to supply all of the fatty acids with sodium hydroxide mates, the soap is considered fully saponified. No discount is taken from the percentage of sodium hydroxide required for complete saponification. This fully saponified soap does not contain excess oils. By using less sodium hydroxide than is required for a complete saponification, however, fat and oil molecules run out of lye mates. The excess oil remains in the final bar of soap as a soothing moisturizer. This milder soap is called a superfatted soap — a soap provided with excess fat and oil to make it more moisturizing.

Nearly all bath soaps clean, but the degree of saponification determines how gently or how harshly they do their jobs. An excess of sodium hydroxide not only can strip the skin of dirt and excess oils, but it can take away important natural oils as well. People with dry skin are especially affected by the strip-clean. When emollient fats and oils are added to soap as superfatting ingredients, they lay a hydrophobic film on the skin’s surface that softens the skin by holding in internal moisture.

So by superfatting our goat milk soap, we are providing our skin with a milder, gentler, and more moisturizing skin-care experience!

In cold process soapmaking, the method I use to make our goat milk soap bars, an acid and a base must be combined to produce soap. It is the reaction that occurs between the acid and base which forms soap. The acid is the oil, whether a neutral oil or a pure fatty acid. The base must be the sodium hydroxide, for fats and oils cannot be converted into soap without it. As the sodium hydroxide and the oils are combined together, the process of saponification occurs as the triglycerides of the oils break down into fatty acids  that react with the sodium ions of the base lye solution to create a whole new product – SOAP!

The proportion of sodium hydroxide to oils in a soap recipe affects how they react…and we use a discounted proportion of sodium hydroxide in order to produce a “superfatted” bar of soap – an extra mild, moisturizing soap. I will share more on what this means in the next blog post. For now, though, you can understand how our soap is made with sodium hydroxide yet contains no chemicals and is very mild and gentle!