Combining BHA Toner Ingredients with Serum: Formulation Challenges and Recommendations

Based on the feedback provided regarding your serum formulation for whitening, acne reduction, and oil control, here's an analysis and suggestions for improvement:

Analysis of the Formula and Texture:

1. Texture: As noted in the replies, with the current ingredients and percentages, the texture will likely be very liquidy, similar to water or a toner ("เหลวหยดติ๋งๆ เหมือน น้ำ"). It will not have the typical viscous feel of a serum. This is because the formula lacks thickening agents.
2. Stickiness: The feedback suggests it won't be sticky but might feel slightly slippery due to the Propylene Glycol (PG).
3. Color: The high percentage of Vitamin B12 (VB12) will give the product a red color.

Suggestions for Improvement and Considerations:

1. Separate BHA: The most critical feedback is the recommendation to separate the BHA into a different product, such as a toner. Combining BHA (which works best at a specific low pH for exfoliation) with other ingredients, especially those like Vitamin B5 (which has a high pH), can complicate pH adjustment for optimal efficacy and stability of all components. Creating a separate BHA toner for exfoliation and a serum/gel for the other beneficial ingredients (Vitamins, N-acetyl Glucosamine, Zinc PCA, Licochalcone A) is a common and often more effective approach.
2. Texture Adjustment (if keeping as one product or for the separate serum): If you want a serum texture, you would need to add a gelling or thickening agent (like Pro Polymer as suggested by staff) to the formula containing the vitamins and other actives (excluding BHA).
3. Vitamin B12 Percentage: The suggestion to reduce VB12 to 2% is worth considering. 5% is noted as quite high and potentially irritating for some skin types, often used for more severe inflammatory conditions. Reducing it would also lessen the intense red color.
4. Propylene Glycol (PG): The purpose of 5% PG was questioned. While it acts as a humectant and solvent, if you aim for a very light, non-slippery feel, you might consider reducing it or using alternative humectants, although 5% is generally considered acceptable and contributes to the "slippery" feel mentioned.
5. Zinc PCA: Note that Zinc PCA's oil-control properties might be more pronounced in formulas with fewer moisturizing components. In your current formula, PG is a humectant, which might slightly affect this, but 1% Zinc PCA is a standard usage rate.
6. pH Management: As pointed out, Vitamin B5 has a high pH. To ensure the efficacy and stability of other ingredients (like Niacinamide, which can convert to Niacin at high pH causing flushing, or Zinc PCA), careful pH adjustment of the final formula (or the separate serum part) would be necessary, likely bringing it down to a slightly acidic to neutral range (e.g., pH 5-6).

Conclusion:

Your current formula, as is, will likely be a watery, red-tinted liquid. To achieve a serum texture and potentially better efficacy/stability, especially for the BHA, the strongest recommendation is to split the formula into two products: a BHA toner and a separate serum/gel containing the vitamins and other actives. If you proceed with a single product, be aware of the watery texture, the red color, and the challenges in optimizing the pH for all ingredients simultaneously.