Why Does Cold Process Soap Change Color During Curing?

Causes of Color Change

The color change in cold process soap during curing is primarily caused by the oxidation of the fatty acids present in the soap. This process, known as saponification, leads to the formation of new compounds that can alter the soap’s color. For example, the oxidation of stearic acid can cause a change from white to yellow or brown.

Factors Affecting Color Change

The rate and extent of color change can be influenced by several factors, including the type and quantity of oils used, the pH level of the soap, and the ambient temperature and humidity during curing. Generally, soaps with a higher percentage of coconut oil tend to darken more quickly than those with a higher percentage of olive oil. Soapers can also influence the color change by controlling the pH level of the soap, as a higher pH can lead to faster oxidation and a more pronounced color change.

Minimizing Color Change

To minimize the color change in cold process soap, soapers can take several precautions. One approach is to use a higher percentage of olive oil, which tends to produce a milder oxidation reaction. Another strategy is to add colorants or oxides that are more stable and less prone to change during curing. Additionally, soapers can control the curing conditions, such as temperature and humidity, to slow down the oxidation reaction and reduce the extent of color change.