Answer to Your Questions

Lightweight Serum Sunscreen

According to the staff's advice, directly mixing SPF Protect Ultra™ with Silky Serum Base is not possible to achieve a lightweight serum sunscreen texture. The staff recommended using Light Cream Maker™ at a concentration of about 1.5-2% instead to create the desired lightweight cream texture. There is also a sample recipe available that uses Light Cream Maker™ and SPF Protect Ultra™.

• SPF Protect Ultra™ II
• Silky Serum Base (Face/Eye)
• Light Cream Maker™

Facial Serum Formula

Regarding the second formula you inquired about, which contains Azelaic acid 10%, pitera 55%, betaglucan 10%, double hyaluronic liquid 10%, Vitamin c 5% (powder), and water, there are several points to consider:

1. Powder Vitamin C (L-Ascorbic Acid): As the staff mentioned, powder Vitamin C (L-Ascorbic Acid) is highly unstable when dissolved in water and requires a very low pH (around 2.0-4.0, but FDA requires cosmetics to have a minimum pH of 3.5) for stability. It also requires a chelating agent (like Disodium EDTA) to prevent degradation. Mixing this type of Vitamin C in a formula with other ingredients that may have a higher pH will likely cause the Vitamin C to degrade quickly and may not be effective. Adjusting the pH low enough for Vitamin C could also make other ingredients unstable or irritate your sensitive skin.
2. Ingredient Concentrations:
   • Pitera (Galactomyces Ferment Filtrate) 55%: This is a relatively high concentration. While it can be used up to 100%, using it in high amounts might feel greasy, which might not be ideal for your skin that is sometimes oily.
   • Betaglucan: Generally, Beta Glucan extracted from oats (like Beta Glucan 70%) is recommended for use at a rate of 0.1-1.0% (1% recommended). Using 10% might make the product texture too thick or sticky and may not be necessary to achieve the benefits.
   • Double Hyaluron Liquid: The Double Hyaluron Liquid product has a Hyaluronic Acid concentration of 5% (2.5% Nano and 2.5% Standard). Therefore, using 10% of this liquid in your formula means using 0.5% actual HA. This might be slightly low for areas of your skin that are dry, but could be acceptable for combination skin.
3. Formula Compatibility and Stability: Mixing several ingredients with different optimal pH ranges at high concentrations can lead to formula instability, separation, or reduced efficacy of the ingredients. This is particularly true with powder L-Ascorbic Acid, which requires a very low pH.
4. Sensitive Skin: Given your sensitive skin, using multiple active ingredients at high concentrations, such as Azelaic Acid 10% combined with Vitamin C (which requires a low pH) and high concentrations of Pitera and Betaglucan, could increase the risk of irritation.

In summary, the second formula you proposed is likely to have issues with stability, ingredient compatibility, and potential skin irritation, especially concerning the unstable powder Vitamin C.

• Azelaic Acid (Liquid Azelaic™)
• Galactomyces Ferment Filtrate (aka Pitera)
• Beta Glucan 70% (Oat Extract, Water-Soluble)
• Double Hyaluron Liquid
• Vitamin C (L-ascorbic acid) (Standard)