Adding Actives to Absolue Soft Cream Base: Viscosity and Preservation
Question
I have the Absolue Soft Cream Base and plan to mix it with active ingredients (water-soluble or oil-soluble). I previously read that adding up to 10% water-soluble active is acceptable. If I add 20% water-soluble active, will the viscosity change significantly, perhaps becoming a lotion? If I add 20% oil-soluble active, will the viscosity change significantly, perhaps becoming too sticky? Given the base is preservative-free, how does adding 20% of either type of active affect its preservation ability? Is there a maximum percentage I can add without needing to add a preservative system to the final product?
Answer
Adding Actives to Absolue Soft Cream Base
Regarding your questions about adding active ingredients at 20% to the Absolue Soft Cream Base:
Adding 20% Water-Soluble Active: Adding a high percentage (20%) of water-soluble active ingredients is likely to significantly decrease the viscosity of the cream base. It could potentially become much thinner, possibly resembling a lotion or even leading to separation, as you are adding a large amount of a water-based component to an existing emulsion.
Adding 20% Oil-Soluble Active: Adding 20% of an oil-soluble active ingredient will also likely change the viscosity. The extent and direction of the change (thicker or thinner) will depend heavily on the specific nature of the oil-soluble active (e.g., a light liquid oil versus a solid or waxy material). It could also make the cream feel heavier or greasier. A 20% addition is quite substantial for a pre-made base.
Effect on Preservation: The Absolue Soft Cream Base is listed as "Preservative-Free". While it contains an antioxidant to help maintain the active ingredients within the base itself, it does not contain a preservative system to protect the final product from microbial contamination once other ingredients are added. Adding 20% of any active ingredient (water-soluble or oil-soluble) significantly dilutes the base and, especially with water-soluble additions, increases the water activity, creating a favorable environment for microbial growth. Therefore, adding 20% of either type of active will compromise the microbial stability of the final product. You must add a suitable preservative system to your final formulation when incorporating additional ingredients at such high percentages to ensure its safety and shelf life. There is no maximum percentage you can add without affecting preservation, as the base itself is preservative-free and requires a preservative system in the final product when modified with other ingredients.
In summary, adding 20% of either water-soluble or oil-soluble actives will likely alter the texture significantly, and critically, you will need to add a preservative to the final mixture to prevent microbial growth.
