Addressing White Residue in Vitamin C Silicone Serum

The white residue you're observing on your fingers after applying the serum is a normal characteristic of this type of formulation. As discussed in the forum, this serum is designed as an anhydrous (water-free) system where the liquid components (Isododecane and silicone) evaporate upon application, leaving the powdered Vitamin C (both L-Ascorbic Acid and Vitamin C Ester) on the skin surface. These powders are then intended to absorb gradually over time.

This mechanism is why a slight powdery feel or visible residue can occur, especially on the fingers used for application. The staff's recommendation to use it before bed is precisely because it allows several hours for this absorption process to take place.

Even without the Vitamin C Ester, L-Ascorbic Acid itself is a powder, and at a high concentration like 15%, it will contribute to the residue once the liquid base evaporates.

How to Minimize Residue

While complete elimination of residue might not be possible due to the nature of the formula, you can try to minimize it:

• Ensure Fine Particle Size: Using the finest grade of L-Ascorbic Acid available (like the Ultra-Fine grade) can help, as smaller particles are less noticeable and may disperse better.
• Thorough Dispersion: Ensure the Vitamin C powders are very well ground and dispersed evenly throughout the Isododecane and silicone mixture. Although they don't fully dissolve, good dispersion prevents clumping.

Impact on Efficacy

The presence of this white residue does not mean the serum is ineffective. It is part of the intended delivery system for the Vitamin C to remain on the skin and be absorbed over time. You can explain this to your friend so they understand why the residue occurs and that it is normal for this product type.

In summary, the residue is expected for this formulation. Focusing on using fine powders and ensuring thorough mixing can help reduce its appearance, but some residue is inherent to the design.