How to Prepare HEC for Serum and Prevent Pilling

The issue of "pilling" or "flaking" (ขุย) when using Hydroxyethyl Cellulose (HEC) in a serum usually stems from incomplete dissolution or using a concentration that is too high for the skin to absorb, leading to a film that peels off when rubbed.

Causes of Pilling (Flaking)

1. Incomplete Dissolution: If HEC is not fully hydrated and dissolved, microscopic particles remain. When the serum dries, these particles appear as flakes.
2. High Concentration: HEC is a film-former. If used at a high percentage (e.g., above 1.5-2% in a leave-on serum), the film becomes thick and prone to peeling.
3. Incompatibility: While HEC is non-ionic and very stable, combining it with high amounts of other film-formers (like certain gums or high-molecular-weight Hyaluronic Acid) can increase the chance of pilling.

Correct and Detailed Preparation Methods

To ensure a smooth, clear gel without pilling, you can use one of the following two methods:

Method 1: The Heat Method (Recommended for this grade)

1. Disperse: Gradually sprinkle the HEC powder into room temperature water while stirring or blending constantly. This prevents the formation of "fish eyes" (clumps that are dry inside).
2. Heat: Heat the mixture to approximately 70°C. HEC dissolves and forms a gel at this temperature.
3. Stir: Continue stirring while heating. Once it reaches 70°C and the solution becomes clear and viscous, turn off the heat.
4. Cool Down: Continue stirring occasionally as it cools down to ensure a uniform texture.

Method 2: The pH Adjustment Method (Faster Dissolution)

HEC dissolves much faster in alkaline conditions (higher pH).

1. Disperse HEC in room temperature water.
2. Adjust the pH of the water to about 8.0 - 9.0 using an alkali (such as Triethanolamine). You will notice the HEC dissolves and thickens almost immediately.
3. Once fully dissolved and clear, adjust the pH back down to the desired level for your serum (typically pH 5.0 - 6.0) using an acid (such as Citric Acid or Lactic Acid).

Tips for a Perfect Serum Texture

• Usage Rate: For a serum, a concentration of 0.5% - 1.0% is usually sufficient to provide a nice slip and viscosity without being too thick or prone to pilling.
• Blending: Use a high-shear mixer if possible to ensure complete dispersion, but be careful not to incorporate too many air bubbles.
• Order of Addition: Add HEC at the beginning of the process (Water Phase) before adding other active ingredients.
• Check Clarity: The final gel should be perfectly clear. If it looks cloudy or has tiny specks, it is not fully dissolved and will likely cause pilling.