Turbidity Issue in Bakuchiol Serum Formulation
Question
I am experimenting with a formula using [url=http://www.myskinrecipes.com/shop/%E0%B8%95%E0%B9%88%E0%B8%AD%E0%B8%95%E0%B9%89%E0%B8%B2%E0%B8%99%E0%B8%A3%E0%B8%B4%E0%B9%89%E0%B8%A7%E0%B8%A3%E0%B8%AD%E0%B8%A2/6976-bakuchiol-natural-retinol.html:22v37e5k]Bakuchiol[/url:22v37e5k] at 0.5%. I mixed [url=http://www.myskinrecipes.com/shop/%E0%B8%AA%E0%B8%B2%E0%B8%A3%E0%B8%A5%E0%B8%94%E0%B9%81%E0%B8%A3%E0%B8%87%E0%B8%95%E0%B8%B6%E0%B8%87%E0%B8%9C%E0%B8%B4%E0%B8%A7/738-peg-40-hydrogenated-castor-oil.html:22v37e5k]PEG-40 Hydrogenated Castor Oil[/url:22v37e5k] 3% and [url=http://www.myskinrecipes.com/shop/%E0%B8%AA%E0%B9%88%E0%B8%A7%E0%B8%99%E0%B8%9B%E0%B8%A3%E0%B8%B0%E0%B8%81%E0%B8%AD%E0%B8%9A%E0%B9%80%E0%B8%84%E0%B8%A3%E0%B8%B7%E0%B9%88%E0%B8%AD%E0%B8%87%E0%B8%AA%E0%B8%B3%E0%B8%AD%E0%B8%B2%E0%B8%87%E0%B8%84%E0%B9%8C/138-propylene-glycol-%E0%B9%82%E0%B8%9E%E0%B8%A3%E0%B9%84%E0%B8%9E%E0%B8%A5%E0%B8%B5%E0%B8%99-%E0%B9%84%E0%B8%81%E0%B8%A5%E0%B8%84%E0%B8%AD%E0%B8%A5.html:22v37e5k]Propylene Glycol[/url:22v37e5k] 3% until combined, then added 10% water. The resulting solution was clear. However, when I added this clear solution to the main water phase (70% water + other active ingredients), it became turbid. Is there a way to fix this?
Answer
Based on the information you provided and the properties of the ingredients, the turbidity you are experiencing when adding your Bakuchiol pre-mixture to the main water phase is likely due to the Bakuchiol coming out of solution or dispersion upon dilution.
Bakuchiol is an oil-soluble ingredient, and while PEG-40 Hydrogenated Castor Oil is a solubilizer, the concentration used (3% in the pre-mixture, which becomes lower in the final 80% water phase) might not be sufficient to keep 0.5% Bakuchiol fully solubilized in the presence of a large amount of water and potentially other active ingredients.
Here are a few ways to address this issue:
- Increase the Solubilizer Concentration: The most common solution for turbidity caused by insufficient solubilization is to increase the amount of the solubilizer. Try increasing the percentage of PEG-40 Hydrogenated Castor Oil in your formula. You might need to experiment to find the minimum concentration that keeps the final solution clear. A higher ratio of solubilizer to Bakuchiol is often needed in the final formula, not just in the concentrated pre-mixture.
- Adjust the Mixing Method: Ensure the Bakuchiol is fully dissolved or dispersed in the PEG-40 Hydrogenated Castor Oil and Propylene Glycol phase before adding it to the water. When adding this phase to the main water phase, do so slowly and with vigorous stirring or blending to help the solubilizer effectively incorporate the Bakuchiol into the water.
- Consider Other Actives: The other active ingredients in your 70% water phase might be interfering with the solubilization. If possible, try making the formula with just Bakuchiol, PEG-40 Hydrogenated Castor Oil, Propylene Glycol, and water to see if it remains clear. If it does, you may need to investigate compatibility issues with the other actives or increase the solubilizer further to account for their presence.
- Check pH: While primarily for stability, ensuring the pH of your final formula is within the recommended range for Bakuchiol (ideally 3.5-6.5) might also indirectly help with clarity or prevent issues over time.
- Consider a Co-solubilizer: The description for Bakuchiol mentions using Propylene Glycol or Dimethyl isosorbide as penetration enhancers. Dimethyl isosorbide is often a very effective solvent/co-solubilizer for difficult-to-solubilize ingredients in water systems. You could consider incorporating Dimethyl isosorbide into your pre-mixture phase.
Start by trying to increase the concentration of PEG-40 Hydrogenated Castor Oil and refining your mixing technique when combining the phases.
