Formulation Advice for Your Serum

Okay, I have reviewed the information about the ingredients you plan to use: L-ascorbic acid (Ultra-Fine), Sodium Hyaluronate, Argireline, Vitamin E (Tocopheryl Acetate), and Ferulic Acid.

Here is the information regarding your questions:

Dissolving L-Ascorbic Acid (Ultra-Fine)

L-ascorbic acid (Vitamin C) is highly effective but also very unstable, especially in water. The Ultra-Fine grade (Product ID: 133) is designed to disperse easily, particularly in water-free (anhydrous) formulations.

• Dissolving in water: While L-ascorbic acid powder can dissolve in water, it is not recommended for stability. It will quickly oxidize and lose its effectiveness when dissolved directly in water.
• Best dissolution method: To maintain the stability and efficacy of L-ascorbic acid, it is best formulated in an anhydrous base (without water) or in a water-based formula with a very low pH (ideally between 2.0-3.5, although cosmetic regulations often require pH 3.5 or higher). Anhydrous systems (like silicone or glycol bases) offer better stability for L-ascorbic acid. In water-based systems, a low pH is crucial, along with the addition of antioxidants like Ferulic Acid and Vitamin E, which help protect L-ascorbic acid from oxidation.

Oxidation of L-Ascorbic Acid in Water

Yes, dissolving L-ascorbic acid directly in water will cause it to oxidize rapidly. This leads to a loss of potency and the solution changing color (often turning yellow or orange). This is why stable L-ascorbic acid serums are typically formulated in anhydrous bases or carefully buffered low-pH water/solvent systems with antioxidants.

Ingredient Concentrations

Let's look at the proposed concentrations:

• L-ascorbic acid 15%: This concentration is within the effective range (typically 3-15%) for L-ascorbic acid to provide antioxidant benefits, stimulate collagen, and help with skin brightening. This concentration is appropriate if formulated correctly for stability.
• Sodium Hyaluronate 25%: This concentration for Sodium Hyaluronate powder (such as Sodium Acetylated Hyaluronate, Product ID: 8240) is extremely high and likely not feasible in a serum. Sodium Hyaluronate is a powerful gelling agent that requires water to hydrate and function. At 25%, it would likely create an unusable, thick, sticky gel or paste rather than a serum, and it would be very difficult to dissolve properly. Typical usage rates for Sodium Hyaluronate powder in serums are much lower, usually ranging from 0.1% to 2%. You should significantly reduce the concentration of Sodium Hyaluronate.
• Argireline 3%: This concentration is within the recommended usage range (3-10%) for Acetyl Hexapeptide-8 (Product ID: 45). Argireline is typically supplied as a water-based solution.
• Vitamin E (Tocopheryl Acetate) 0.1%: This concentration is within the recommended range (0.1-1%). At 0.1%, it functions well as an antioxidant to protect the formula. If you intend it to also provide significant antioxidant benefits to the skin, a slightly higher concentration (e.g., 0.5%) could be considered, but note that higher amounts (>0.5%) can feel sticky. Vitamin E Tocopheryl Acetate (Product ID: 65) is oil-soluble.
• Ferulic Acid 0.1%: The recommended usage rate for Pure-Ferulic Acid (Product ID: 131) for anti-aging/anti-oxidation in skincare is 0.5-1%. While 0.1% might offer some protection to the formula itself, it is likely too low to provide optimal benefits to the skin, especially when paired with 15% L-ascorbic acid. Increasing this to 0.5% or 1% would enhance the serum's antioxidant power and stability, similar to well-known formulations like SkinCeuticals CE Ferulic (Product ID: 70). Ferulic Acid is not water-soluble and requires solvents like Ethoxydiglycol or ethanol.

Ingredient Compatibility Challenge: Your proposed list includes ingredients that require water to dissolve/function (Sodium Hyaluronate, Argireline) and ingredients that are unstable in water or require specific solvents (L-ascorbic acid, Ferulic Acid, Vitamin E). Creating a stable, homogenous serum with all these ingredients at effective concentrations presents a significant formulation challenge.

Achieving Light Texture in Anhydrous Formulations

If you choose an anhydrous base (which is better for L-ascorbic acid stability), achieving a light, non-greasy feel depends heavily on the choice of base ingredients.

• Using lightweight, volatile silicones (like Cyclopentasiloxane or low-viscosity Dimethicone) can provide a smooth, silky texture that feels lightweight and non-greasy on the skin due to the use of volatile silicones.
• Using specific glycols or esters that have a lighter feel can also help. Ethoxydiglycol, often used as a solvent for Ferulic Acid and L-ascorbic acid in anhydrous or low-water formulas, can contribute to a lighter feel compared to heavier glycols.
• Ensuring the L-ascorbic acid powder is well-dispersed (the Ultra-Fine grade helps with this) is also crucial to avoid a gritty or powdery texture.

Silicone vs. Glycol Bases for Anhydrous/Low-Water Formulas

Both silicone and glycol-based systems can be used for L-ascorbic acid serums, each with pros and cons:

• Silicone Base (like Kiehl's):
  • Pros: Excellent for creating a smooth, silky texture that feels lightweight and non-greasy on the skin due to the use of volatile silicones. Provides good dispersion for powders like L-ascorbic acid. Offers good stability for L-ascorbic acid in an anhydrous environment.
  • Cons: Silicones do not provide hydration themselves (though they reduce water loss). Some users prefer to avoid silicones. Incorporating water-soluble ingredients like Sodium Hyaluronate and Argireline into a silicone base is difficult.
• Glycol Base (like SkinCeuticals):
  • Pros: Glycols (like Propylene Glycol, Butylene Glycol, Ethoxydiglycol) can act as solvents for actives and provide some humectant (moisture-binding) properties. A blend of glycols and a small amount of water at a low pH is a proven system for stabilizing L-ascorbic acid, especially when combined with Ferulic Acid and Vitamin E (Product ID: 70 is an example of this type of formula). Ethoxydiglycol is particularly useful for dissolving Ferulic Acid.
  • Cons: Glycols can sometimes feel slightly sticky or warm on the skin depending on the type and concentration. Requires careful pH control for L-ascorbic acid stability. Incorporating high concentrations of gelling agents like Sodium Hyaluronate can still lead to texture issues.

In summary, dissolving L-ascorbic acid in plain water is not advisable due to oxidation. An anhydrous or low pH water/solvent system is necessary for stability. Your proposed concentrations need significant adjustment, particularly the Sodium Hyaluronate. Combining all your desired ingredients into a single, stable, light-textured serum is challenging due to their different solubility requirements. You might need to simplify the formula, use alternative ingredient forms, or employ advanced formulation techniques.