Troubleshooting Lumps in Cold Process Cream with Sodium Polyacrylate (Cosmedia SP)

Question

I am formulating a cream using the cold process method with Sodium Polyacrylate (like Cosmedia SP) as the thickener and emulsifier. My formula includes 10% Limnanthes alba seed oil.

However, I am encountering an issue where the finished cream has small lumps. I was previously advised that this might be due to incompatibility with Polysorbate 20 and Allantoin, and was recommended to remove Polysorbate 20 and replace DMDM Hydantoin with Phenoxyethanol.

Could you please provide detailed advice on why these lumps are forming and how to prevent them, specifically focusing on the proper technique for incorporating Sodium Polyacrylate in a cold process formulation? Also, please confirm the recommendation regarding Polysorbate 20 and the suggested preservative alternatives (Phenoxyethanol, Phenoxyethanol SA), including their usage percentages and addition conditions.

MySkinRecipes Expert · Accepted Answer

Advice on Making Cream with Sodium Polyacrylate (Cosmedia SP)

Based on your formula and the previous discussion, the issue of small lumps in your cold-process cream using Sodium Polyacrylate (like in Cosmedia SP) likely stems from the Sodium Polyacrylate not hydrating and dispersing properly in the water phase.

Sodium Polyacrylate is a polymer that functions as both a thickener and an emulsifier in cold-process formulations. It works by swelling in water and creating a gel-like network that stabilizes oil droplets within the water phase.

Addressing the Lumping Issue:

The presence of small lumps indicates that the Sodium Polyacrylate did not hydrate and disperse properly. While incompatibility with Polysorbate 20 and Allantoin was suggested, another common cause for lumping with this type of ingredient is insufficient mixing or improper addition technique.

Proper Dispersion: Sodium Polyacrylate powder needs to be added to the water phase in a way that allows each particle to be surrounded by water without clumping. "Sprinkling" or "raining" the powder onto the surface of the water while stirring vigorously is a common technique to prevent lumps.
Sufficient Mixing/Shearing: After adding the powder, thorough mixing is crucial for the polymer to fully hydrate and swell. While homogenization helps, the initial mixing when combining Part A and Part B is critical. Ensure continuous and effective mixing as you add the water phase to the oil phase containing the dispersed Sodium Polyacrylate. The description for Light Cream Maker (which contains Sodium Polyacrylate) also notes that insufficient blending or stirring can lead to a flaky or lumpy texture.

Regarding Polysorbate 20:

The suggestion to remove Polysorbate 20 is likely because Sodium Polyacrylate is designed to emulsify the oil phase on its own. Adding another emulsifier like Polysorbate 20 might interfere with the primary emulsification mechanism of the Sodium Polyacrylate, potentially contributing to instability or texture issues like lumping. Sodium Polyacrylate should be sufficient to emulsify 10% Limnanthes alba seed oil.

Replacing DMDM Hydantoin:

DMDM Hydantoin is a formaldehyde-releasing preservative, and safer alternatives are often preferred. As suggested, Phenoxyethanol is a good option:

Phenoxyethanol (Extra Pure): A widely used preservative effective against bacteria, though less so against fungi. Use at 0.5-1.0% and mix in below 80°C.
Phenoxyethanol SA (eq. Optiphen Plus): A broad-spectrum blend (Phenoxyethanol, Caprylyl Glycol, Sorbic Acid) offering better protection against fungi. Use at 0.5-1.25%, add in the final step below 60°C, best pH 2.0-6.0.

Choose based on desired preservation spectrum and final formulation pH.

In summary, to address lumping, focus on the technique of adding Sodium Polyacrylate with vigorous mixing and ensure sufficient mixing during emulsification. Removing Polysorbate 20 is recommended. For preservation, Phenoxyethanol or Phenoxyethanol SA are safer alternatives.