Sodium lactate in soap is commonly used to harden the resulting soap bar. There are many ways to affect the hardness of your bar, but sodium lactate in soap is very popular. At a usage rate of 1 teaspoon per pound of oils in your base soap making recipe, it is economical and a bottle lasts a long time. Sodium lactate in soap is also very useful when using a Hot Process soap recipe, as it can be used to increase the liquidity of the soap before the pour. Made from the fermentation of sugars naturally occurring in beets and corn, sodium lactate is the sodium salt of lactic acid.

There are other options for increasing the hardness of your soap beyond sodium lactate. In soap making, you can use 1 tablespoon of sodium chloride — that’s plain old table salt, per pound of base oils to harden your bar. Dissolve the salt in a warm solution of water and lye for soap. Using a soap making recipe with palm oil, coconut oil, stearic acid (a fatty acid derived from palm kernel oil), or beeswax will result in a harder bar. For stearic acid, a naturally vegetable-derived waxy substance, .5 ounce per pound of oils is sufficient to produce a hard soap. More than this, and the soap may crumble, crack or have less lathering ability. For beeswax, a usage rate of .5 oz per pound of base oils is sufficient. This is most likely due to high content of unsaponifiable ingredients, or ingredients that cannot be turned into soap. When using beeswax, be careful to use a cool recipe and watch for overheating. The things that tend to harden a soap also can decrease lather if too much is used, so it is important to go by the recommended usage rates.

Above: This honeysuckle soap was created using honey in the lye water to aid the lather. The lye water was slightly too hot, resulting in a darkening of the sugars and a resulting caramel-colored soap. Photo by Melanie Teegarden.

In addition to the variety of soap ingredients that can harden your bar, there are a variety of ways to introduce sugars to a soap recipe that will increase the luxuriousness of the lather. You can simply add I tablespoon of plain sugar to your warm lye water prior to mixing. The lye mixture must be room temperature, cold or warm — not hot — to avoid scorching the sugars, which will cause a darkening of the soap. Fruit juices, milk, and coconut water are also options that can be used to replace some or all of the water called for in a recipe. To add sugars to your soap with these methods, freeze the juice, milk or water and use the frozen cubes to dissolve the lye slowly, stirring to prevent scorching as the liquid melts. Be prepared for fruit juices to lose or change color when introduced to the lye.

Honey soap benefits the lather beautifully, as well. To make soap using honey, it is recommended that you use no more than one tablespoon of honey per pound of base oils in your recipe. Honey soap benefits from cool temperatures and cold (or room temperature) lye water. Because the honey does not mix with oils, there are two ways you can add it to the recipe. First is to dissolve it in the cold lye water before mixing the soap batter. Second, you can add the honey to the soap batter at trace — again, use cool temperatures and be prepared for quick thickening. If you use too much honey, it can result in seizing and superheating of your recipe.

Above: A selection of common soap additives. Salt, sugar, sodium lactate, activated charcoal, and pink kaolin clay. There are also common additives that affect the finished color of your soap, including titanium dioxide, kaolin and other clays, and cosmetic muds such as dead sea mud. Titanium dioxide is used to make a bright white, opaque bar of soap. Kaolin clay, which has some soap lightening ability, is mostly used as a scent fixative. Other clays can range in color from mustard yellow to brick red to purple, and can be used for coloring soap naturally and adding a “slippery” quality to the lather. To prevent glycerine rivers in a titanium dioxide or clay-containing soap, hydrate the powder with a small amount of water before adding. This helps to prevent a moisture imbalance in the finished soap which can result in crackling, a harmless cosmetic blemish that some consider quite beautiful. To use cosmetic muds, hydration with a touch of water is also a good idea. Be aware that muds tend to be rather gritty and will add an exfoliating effect to your soap.

There you have it — a wide variety of easy-to-find additives to improve the qualities of your handmade soap. What have you tried adding to your home soap making recipe? Share your results!