Reducing Foaming in Serum Formulation

Causes of Foaming

1. Air Entrapment During Mixing: The most common reason for foaming in a serum like yours is air being incorporated during the mixing process. When you mix ingredients, especially if you do so vigorously or at high speed, air bubbles can get trapped within the liquid.
2. Stabilization by Thickener: Your formula includes Xanthan Gum, which is a very effective thickener. A property of many thickeners, including Xanthan Gum, is that they can stabilize foam. Once air bubbles are created during mixing, the Xanthan Gum forms a gel network that prevents these bubbles from rising and popping, leading to persistent foam.
3. Ingredients Reducing Surface Tension: While your serum doesn't contain traditional surfactants (like those in cleansers), some ingredients can slightly reduce the surface tension of the water phase. Ingredients like Glycerin, Propylene Glycol, Sodium Hyaluronate, Panthenol, MOIST24 (Glycereth-26), and particularly Siliwax Aqua (Bis-PEG-18 Methyl Ether Dimethyl Silane, which acts as a solubilizer/emulsifier) can contribute to lowering surface tension. When you rub the serum on your skin, this slight reduction in surface tension can facilitate the formation of small bubbles, which are then stabilized by the Xanthan Gum.

Solutions to Reduce Foaming

1. Gentle Mixing:

   • Reduce the speed and intensity of your mixing. Stir gently rather than whipping or using a high-shear mixer for extended periods.
   • Mix ingredients in a way that minimizes air incorporation. For example, when adding powders like Xanthan Gum or Niacinamide to water, sprinkle them slowly onto the surface and allow them to hydrate before stirring, or create a slurry with a small amount of glycerin or propylene glycol first.

2. De-aeration (Letting it Rest):

   • After mixing, let the serum sit undisturbed for a significant amount of time. This could be several hours or even overnight. Trapped air bubbles will slowly rise to the surface and dissipate.
   • You can gently tap the bottom of the container on a surface to encourage bubbles to rise.

3. Consider an Anti-Foaming Agent (Use with Caution):

   • If gentle mixing and resting are not enough, you could consider adding a very small amount of a cosmetic-grade anti-foaming agent. These are specifically designed to destabilize foam bubbles.
   • Silicone-based anti-foaming agents are common. However, you must use these at very low concentrations (often fractions of a percent) and test carefully to ensure they don't affect the clarity, stability, or feel of your serum. Adding too much can cause other issues.

4. Review Xanthan Gum Concentration: While you haven't provided percentages, ensure you are using Xanthan Gum at the minimum effective concentration needed to achieve your desired viscosity. Higher concentrations will create a more stable gel network, which is better at trapping foam.

Focusing on gentle mixing and allowing the serum to rest after preparation are usually the most effective first steps to eliminate excessive foaming.