Vitamin C Serum: Formulation, Stability, and Maximising Potency

Vitamin C, or ascorbic acid, is one of the most celebrated skincare ingredients due to its antioxidant properties, collagen-boosting ability, and brightening effects. But formulating a stable, effective Vitamin C serum is not straightforward—its potency can degrade quickly if not handled correctly. In this article, we’ll explore Vitamin C formulations, derivatives, stability challenges, and tips for making an effective serum.

Why Vitamin C is Popular in Skincare

Vitamin C benefits the skin in multiple ways:

• Antioxidant protection: Neutralises free radicals from UV exposure and pollution.

• Collagen synthesis: Stimulates fibroblasts to produce collagen, improving firmness.

• Brightening effect: Reduces hyperpigmentation and evens out skin tone.

• Anti-inflammatory: Calms redness and supports skin repair.

Despite these benefits, Vitamin C is highly unstable, especially in water-based formulations, which presents a major challenge for serum development.

Common Vitamin C Derivatives in Skincare

Pure L-ascorbic acid is highly potent but unstable. Derivatives are often used to improve stability and penetration:

Key takeaway: The choice of derivative affects serum stability, skin penetration, and pH requirements.

Stability Challenges of Vitamin C Serums

Vitamin C is prone to oxidation, which causes it to turn yellow or brown, losing effectiveness. Factors affecting stability:

• pH: L-ascorbic acid is most stable at pH < 3.5.

• Exposure to air: Oxygen accelerates degradation.

• Light exposure: UV light promotes oxidation.

• Temperature: High temperatures reduce potency quickly.

• Water content: Pure L-ascorbic acid in aqueous solutions is more unstable.

Signs of oxidation: Discolouration, unpleasant smell, reduced effectiveness.

Choosing the Best Vitamin C Form for a Serum

• For beginners: Derivatives like SAP or MAP are safer, more stable, and gentle for daily use.

• For anti-ageing and deep penetration, Oil-soluble forms like THD or ATIP are ideal.

• For maximum potency: L-ascorbic acid at 10–20% in stabilised formulations, stored in dark, airtight bottles.

Tip: Combining Vitamin C with ferulic acid and vitamin E improves stability and doubles antioxidant efficacy.

Formulation Guidelines

Typical Vitamin C Serum Composition:

• Active Vitamin C (L-ascorbic acid or derivative): 5–20% depending on skin tolerance

• Vehicle/Base: Water (for SAP/MAP) or light oils (for ATIP/THD)

• Stabilisers: Ferulic acid, EDTA, glycerin, or sodium metabisulfite

• pH adjustment: pH 3–3.5 for L-ascorbic acid; derivatives are less strict

• Packaging: Dark glass bottles, airless pumps to minimise oxidation

Process Summary:

1. Dissolve Vitamin C in the chosen vehicle (water or oil) under low heat if needed.

2. Add stabilisers and other actives carefully.

3. Adjust pH if necessary.

4. Package in airtight, dark containers immediately.

Tips to Maximise Serum Potency

• Store in a cool, dark place. Refrigeration prolongs shelf life.

• Use airless pumps or dark dropper bottles to limit oxygen exposure.

• Avoid mixing with high pH ingredients like strong AHAs or baking soda, which can destabilise Vitamin C.

• Combine with antioxidants like Vitamin E and ferulic acid for enhanced stability and efficacy.

• Start with lower concentrations if you have sensitive skin and gradually increase.

Common Issues and How to Prevent Them

Key Takeaways

• Vitamin C is highly beneficial but sensitive to light, air, and pH.

• Choosing the right derivative and formulation ensures stability and potency.

• Oil-soluble derivatives are best for deep penetration, while water-soluble forms are ideal for gentle daily use.

• Packaging, storage, and combination with antioxidants are critical to maintaining effectiveness.

With the right formulation and careful handling, a Vitamin C serum can transform skin health, offering brighter, firmer, and more resilient skin.