Formula Review and Precipitate Issue

Your formula for combination-dry skin targeting brightening, clarity, moisture, firmness, and reduced pores seems well-designed, incorporating several beneficial ingredients:

• GlucoBright™ (Acetyl Glucosamine) and Safe-B3™ (Vitamin B3, Niacinamide) work together effectively for whitening, reducing dark spots, and improving skin hydration and barrier function. Vitamin B3 also helps regulate oiliness and is suitable for acne-prone skin.
• Hi-EGCG™ (Green Tea Extract) provides antioxidant and anti-inflammatory benefits, helps reduce oil production, and can improve skin elasticity.
• Pal-GHK, Pal-GQPR (eq Matrixyl 3000) is included for its anti-aging properties, stimulating collagen synthesis to reduce wrinkles and improve firmness.
• Zinc PCA is a good addition for combination skin as it helps control oiliness, accelerates acne scar healing, and has anti-inflammatory properties.
• Licorice Extract (Glabridin 4.5%, Water-Soluble) contributes to whitening and helps soothe irritation, which can be beneficial for skin with minor acne.

The Double Hyaluron Liquid base provides hydration. As noted by the staff, for combination skin, you might find it beneficial to adjust the base by mixing it with a plain gel base if the T-zone becomes too oily, although the addition of Zinc PCA should help balance this.

Regarding the Matrixyl (Pal-GHK, Pal-GQPR) concentration, you are using 8%, which is above the recommended usage rate of 3-5%. While higher concentrations might be used in some formulations, the typical recommended range for optimal results and stability is 3-5%. It's worth being mindful of this.

Time to See Results

Visible results, particularly brightening and improvement in skin clarity, typically take time as they depend on the skin's natural cell turnover cycle, which is about 28 days. With consistent use of a formula containing effective ingredients like Acetyl Glucosamine, Vitamin B3, and Licorice extract, you might start seeing noticeable improvements in brightening and evenness within 4-8 weeks.

Precipitate Issue

The precipitate you observed after refrigerating the formula is likely due to one of the ingredients having reduced solubility at cold temperatures. Based on the discussion and the properties of common cosmetic ingredients, Allantoin, which is often included in gel bases like the Double Hyaluron Liquid, has low solubility in cold water. When the formula is refrigerated, the Allantoin may crystallize out of the solution, forming a precipitate.

This precipitate is generally not harmful, and the formula is still safe to use. You have a couple of options:

• Filter it out: You can strain the mixture using a fine filter, such as a coffee filter, to remove the solid particles.
• Ignore it: You can simply use the product as is, being aware that there are solid particles present. Shake the bottle before use if needed.

As advised previously, avoid warming the mixture to redissolve the precipitate, especially since your formula contains peptides (Matrixyl), which can be sensitive to heat and may degrade, reducing their effectiveness.