Sodium lactate is becoming a popular soap additive among those who produce homemade soaps. Many cold- and hot-process soap makers, including myself, have found sodium lactate to be beneficial in several ways.
What is it?
Sodium lactate is found naturally in some foods, and is a salt derived from lactic acid. It is most commonly produced from fermenting corn or beets. The finished product is a smooth, clear liquid that has very little odor. Sodium lactate is readily available from soap ingredient suppliers or food additive distributors. For soap making, a 60% solution is ideal, and soap supplies usually stock this concentration. Sodium lactate has a relatively low price; usually less than .30 per ounce.
What does it do in soap?
Sodium lactate contributes several functions to a soap recipe. First of all, it is a humectant, meaning it draws moisture to itself. When used in cold-process or hot-process soap, sodium lactate increases the amount of moisture the user's skin is able to attract and hold. It also helps form a harder bar, allowing the soap to be cut sooner and increasing the life of the soap in the shower or bath. For soaps poured into individual molds, sodium lactate may improve the appearance of the finished soap, and ease in the unmolding of the batch. Hot-process soap makers have discovered that sodium lactate in a recipe aids in keeping the batter fluid and allows easier swirling, pouring, and unmolding. Many soapers also feel that sodium lactate helps preserve the soap, adds creaminess to the lather, and may also serve as a pH balancer.
How do I use it?
Adding sodium lactate to a recipe is simple. There is no need to change any of the oils, lye amount, or liquid amount. Sodium lactate is water soluble, and is added to the liquid/lye solution at the beginning the soap making process. Usual usage rates are between 1% and 3% of the total recipe, depending on the effect desired. For a recipe that usually yields a bar in need of only a little more firmness, 1% may be sufficient. For a softer soap, sodium lactate may be added up to 3%. Too much sodium lactate may result in a crumbly soap, so use only what is necessary. Generally speaking, .5 oz of sodium lactate per pound of oils is a good starting point. So, if your recipe uses 32 ounces of oils, you would add 1 ounce of sodium lactate to your lye/water solution and proceed with soap making as usual.