Formulation Advice for Dark Spot Serum

Thank you for your question regarding your proposed serum formulation for reducing dark spots.

You've listed the following ingredients:

• Stabilized Vitamin C (Natural-C Glycol) Serum
• Satin Cream Maker
• Purified Water
• Phenoxyethanol SA (preservative)

Regarding the compatibility of these ingredients and recommended percentages:

The primary challenge with your proposed formula lies with the Stabilized Vitamin C (Natural-C Glycol) Serum. According to the product information, this specific Vitamin C product is designed to be used as a finished product (100% usage rate) and is not suitable for mixing with additional ingredients, except for small amounts of perfume or coloring. Mixing other components into this serum is not recommended and may compromise its stability and effectiveness.

Therefore, creating a custom formulation by adding Satin Cream Maker, Purified Water, and Phenoxyethanol SA to this specific Vitamin C serum is not advisable based on the product's intended use.

• Satin Cream Maker: In a typical formulation where it is suitable, Satin Cream Maker acts as an emulsifier and thickener, used at 0.1-3.0% (recommended 1-1.5%). It is dispersed in the water phase. It works well in a pH range of 3-12.
• Purified Water: This is the base solvent for many cosmetic formulations.
• Phenoxyethanol SA: This is a broad-spectrum preservative used at 0.5-1.25%. It should be added in the final step at temperatures below 60°C and is effective in a pH range of 2.0-6.0.

pH Adjustment:

The Stabilized Vitamin C (Natural-C Glycol) Serum itself has a low pH (2-3). In general cosmetic formulations, pH adjustment is often necessary for stability, efficacy, and skin compatibility. For ready-made cosmetic products, the pH must be adjusted to at least 3.5 according to FDA regulations. However, since the Vitamin C serum you mentioned is not intended for mixing, the question of pH adjustment for this specific combination is not applicable.

Recommendation:

If you wish to create a custom dark spot reduction serum, it is recommended to use a form of Vitamin C that is supplied as a raw ingredient specifically intended for use in formulations, rather than a finished serum product like the Natural-C Glycol Serum. You can then build your formula around this raw ingredient, incorporating an emulsifier like Satin Cream Maker (if creating a cream/lotion), Purified Water as the base, and a suitable preservative like Phenoxyethanol SA, while carefully considering the compatibility and optimal pH range for all chosen ingredients.

In summary, the specific combination of ingredients you proposed is not recommended due to the nature of the Stabilized Vitamin C (Natural-C Glycol) Serum being a finished product.