What Causes White Ash on Goat's Milk Soap?

Goat's milk soap is known to moisturize and rehabilitate the skin.

Using your own handmade goat's milk soap in place of a commercially manufactured bar purchased at the grocery store holds several benefits to the health of your skin. Milk in general contains animal fats and natural vitamins and emollients (a medicinal substance used to soften and relax the skin), all of which are good for the skin. However, goat's milk in particular is the only milk to contain capric-caprylic triglyceride, an ester composed of a combination of fatty acids known to rapidly penetrate and moisturize the skin. During the handmade creation of goat's milk soap, once you pour the heated liquid into your soap molds and the solution begins to solidify, a white, powdery residue often forms on the top of the soap.

What It Is

The white chalky substance that forms on top of fresh, homemade soap is actually sodium carbonate, more popularly known as soda ash. Sodium carbonate is a sodium salt of carbonic acid, a crystalline substance that forms into the white, powdery substance of "soda ash" as the water in the solution evaporates, a process known as efflorescence.

What Causes It

Soap is formed through saponification, a process in which fats (in this case, fat from the goat's milk) react with an alkaline base (most commonly sodium hydroxide, or lye) to form a solidified bar. When the liquid is placed in the soap molds and left to harden, the sodium in the solution reacts with carbon dioxide in the air and forms a thin layer of soda ash on the top of the soap (hence the name, sodium carbonate).

How to Prevent It

Simply using plastic wrap to cover the soap after the solution is poured into the mold will prevent soda ash from forming (as the layer of plastic cuts the solution off from the open air). Nevertheless, soda ash is completely harmless and washes away after the bar of soap's first use. In fact, the substance is often used inside the home as a cleaning agent (with detergent and used to clean off coffee and espresso machines).

References

• Goatworld.com: Why Goat Milk?
• MetaGlossary.com: Definitions for "Caprylic/Capric Triglyceride"
• Almavi Skincare: Goat Milk Benefits
• NewEnglandGrown.com: Why Goat Milk Soap?
• Wise Geek: What is Soda Ash?

Resources

• Goat Milk Specialties