Advice on Thyme Kill™ Precipitation in Water-Based Formula

You're seeing white particles form when adding your Thyme Kill™/Propylene Glycol mixture to your water-based spray formula. This is a common issue related to the solubility of Thyme Kill™ (o-Cymen-5-ol).

Here's the likely explanation and some advice:

• Solubility: Thyme Kill™ is readily soluble in Propylene Glycol, especially when heated, which is why your mixture becomes clear at 70°C. However, Thyme Kill™ has limited solubility in water.
• Precipitation: When you add the hot Propylene Glycol solution to the cooler water-based formula, two things happen: the temperature drops, and the concentration of water increases significantly. Both of these factors reduce the solubility of Thyme Kill™ in the mixture, causing it to precipitate out as white particles.
• Recommended Method: The product description for Thyme Kill™ suggests dissolving it in Propylene Glycol at a 1:10 ratio (1g Thyme Kill™ per 10g Propylene Glycol), which you are already doing correctly for preparing the concentrate.
• Adding to Water Phase: To minimize precipitation when adding to the water phase, try the following:
  • Allow the Thyme Kill™/Propylene Glycol mixture to cool down to room temperature before adding it to your water-based formula.
  • Add the cooled mixture slowly to the water phase while stirring continuously and vigorously to help disperse it as much as possible.
• Final Concentration: Even with proper mixing technique, if the final concentration of Thyme Kill™ in your water-based formula exceeds its solubility limit in that specific water/glycol ratio at room temperature, precipitation will still occur. Ensure your final formula concentration of Thyme Kill™ is within the recommended usage rate (typically 0.05-0.1%). However, even within this range, solubility can be a challenge in purely water-based systems without additional solubilizers.

In summary, the white particles are likely precipitated Thyme Kill™ because its solubility limit is exceeded when diluted and cooled in the water-based formula. Adding the cooled PG solution slowly with good mixing may help, but the inherent water solubility limit is the primary factor.