Formulation Analysis and Recommendations

Here are the answers to your questions regarding your serum formulation with a target pH of 3.5:

1. Compatibility of Prebio-care and Yeast Radiance at pH 3.5

Based on the product information:

• Prebio-care is recommended for use in formulas with a pH range of 4-10.
• Yeast Radiance is recommended for use in formulas with a pH range of 4.0-6.5.

Including these ingredients in a formula with a target pH of 3.5 is outside their recommended stable and effective pH ranges. While they might not immediately degrade, their long-term stability and efficacy could be compromised at this lower pH. It is generally best to formulate within the recommended pH ranges for optimal performance and shelf life.

2. Effect of pH 4 on Ampho-Glycolic Efficacy

Ampho-Glycolic is a form of Glycolic Acid complexed with Arginine, designed to reduce irritation while maintaining efficacy. The product description indicates that it is effective for skin exfoliation. Glycolic Acid is typically most effective at lower pH values (below 4.0), where a higher percentage exists in its free acid form, allowing for better penetration and exfoliation.

While a pH of 3.5 is closer to the optimal range for free acid exfoliation, a pH of 4.0 is still within a range where Glycolic Acid can be effective, especially with a timed-release component like Encapsulated Salicylic Acid also present. Ampho-Glycolic is specifically designed to be less irritating than standard Glycolic Acid at lower pH levels, suggesting it is intended for use in acidic formulations. At pH 4, Ampho-Glycolic should still provide significant exfoliation benefits, though potentially slightly less intensely than at pH 3.5, while likely being less irritating than standard Glycolic Acid at the same pH.

3. Mixing with a Hand Blender

Yes, you can use a hand blender to mix this formula, especially for dispersing the powder ingredients into the water phase. However, be mindful of the following:

• Aeration: Hand blenders can incorporate a lot of air bubbles into the mixture, which can be difficult to remove and may affect the final product's appearance. Try to keep the blender head submerged and avoid lifting it out of the liquid while mixing.
• ThixoGel: The product description for ThixoGel states that it requires heat (not exceeding 80°C) and continuous stirring to dissolve completely and form a clear, thick gel. A hand blender can provide the stirring, but you will need to heat the water phase appropriately before adding the ThixoGel and mixing. Ensure the ThixoGel is fully dissolved before proceeding.

For best results, especially with ingredients requiring specific mixing conditions like ThixoGel, using a magnetic stirrer with heating capabilities might offer more controlled mixing and heating.

4. Texture and Absorption

Based on the ingredients and their percentages:

• ThixoGel (1%): This will act as the primary gelling agent, creating a thixotropic gel texture. This means the serum will be relatively thick when still but will thin out and become more fluid when shear is applied (like rubbing it onto the skin), allowing for easy spreading.
• HumecMax (5%): As a highly effective humectant, HumecMax will draw and hold moisture, contributing to a hydrating feel on the skin. At 5%, it will provide significant moisturization, which might result in a slightly tacky or substantive feel after application, depending on the overall formula.
• Dimethyl Isosorbide (DMI) (3%): DMI is a penetration enhancer and solvent. It can help the active ingredients absorb better into the skin and can improve the feel of the formula, often making it feel less sticky and more spreadable.

Overall, the formula is likely to have a gel texture that spreads easily due to the thixotropic nature of ThixoGel and the presence of DMI. It should absorb reasonably well, leaving the skin feeling hydrated due to HumecMax. The final feel will be a balance between the gelling effect, the moisturizing feel of the humectant, and the enhanced spreadability from the DMI.