Saponification Cleansing Cream Texture Instability Issue

Suggestions for Improving Your Saponification Cleansing Cream Formula

Based on the issues you're encountering with your saponification facial cleansing cream formula using Stearic acid, Myristic acid, Lauric acid, and Beeswax with KOH, there are two main points to consider: the excessive thickening at high temperatures and the liquefaction at room temperature.

Causes of the Problems:

1. Excessive thickening at 75°C: When adding KOH to the heated mixture of fats and waxes at high temperatures, the saponification reaction occurs rapidly, forming potassium salts of fatty acids (Potassium Soaps). Soaps derived from saturated fatty acids like Stearic acid, Myristic acid, and Lauric acid tend to form thick, gel-like structures particularly well at higher concentrations and temperatures. Additionally, Beeswax (Natural White Beeswax has a melting point around 62°C) is melted at this temperature and contributes to the thick texture when hot.
2. Liquefaction at 25°C: This issue is related to a property of soaps called the Krafft Point, which is the temperature at which the soap becomes fully soluble in water. As the temperature drops below the Krafft Point, the solubility of the soap decreases, causing it to precipitate or form a weaker structure. This results in the product becoming liquid like a lotion or water. Soaps derived from longer-chain saturated fatty acids like Potassium Stearate (from Stearic acid) generally have higher Krafft Points than soaps from shorter-chain fatty acids like Potassium Laurate (from Lauric acid) and Potassium Myristate (from Myristic acid). At 25°C, which is also below the melting point of Beeswax, the Beeswax solidifies and can no longer help maintain the cream's structure as it did when melted.

Other ingredients in your formula, such as Glycerin (Glycerin (USP/Food Grade)) and Polyethylene Glycol (Polyethylene Glycol 400, Snail Resin (PEG-90M)), are humectants and may help adjust texture to some extent, but the primary stability of the cream in a soap system depends on the type and ratio of fatty acids and the resulting soaps. EDTA (Disodium EDTA) acts as a chelating agent, important for soap stability in hard water, which is beneficial for a soap formula.

Possible Solutions:

1. Adjust the Fatty Acid Ratio: Try increasing the proportion of Lauric acid (Lauric Acid (99%)) and Myristic acid (Myristic Acid (FEMA-2764)) while decreasing the proportion of Stearic acid (Stearic Acid). Using more shorter-chain fatty acids will help lower the Krafft Point of the soap mixture, allowing the soap to remain soluble and maintain its structure better at room temperature.
2. Add Co-emulsifiers/Stabilizers: Although the saponified fatty acids act as emulsifiers, adding non-ionic co-emulsifiers or other thickeners compatible with a soap system and high pH can help enhance emulsion stability and maintain viscosity over a wider temperature range. Consider fatty alcohols like Cetyl Alcohol or Cetearyl Alcohol, non-ionic emulsifying waxes (such as Emulsifying Beeswax), or alkali-stable polymeric thickeners.
3. Verify KOH Quantity: Ensure the amount of KOH used is appropriate for the total amount of fatty acids in your formula to achieve complete saponification without excess alkali, which can affect texture and stability.
4. Optimize Manufacturing Process: Controlling the temperature and stirring rate during and after the addition of KOH might help achieve a more uniform cream structure during cooling.

Experimenting by adjusting the fatty acid ratios and adding co-emulsifiers/stabilizers gradually, and observing the results at room temperature, will help you improve the stability of your facial cleansing cream.