Potential Causes for Sedimentation

• Essential Oil Solubility: Essential oils are not water-soluble. Without using heat or a proper solubilizer, the essential oil (EO) at 0.5% will not fully incorporate into the water-based shampoo formula and will likely separate over time, causing cloudiness or settling at the bottom.
• Xanthan Gum Hydration: While you are using Glycerin to help disperse the Xanthan Gum before adding it to water (which is the recommended method), incomplete hydration of the gum can still occur if not mixed thoroughly or if the amount of Glycerin isn't sufficient for the total gum concentration (1.5%). This can lead to undissolved particles settling.
• Ingredient Compatibility/Mixing Order: Even without heat, the order and method of adding ingredients are important. Ensuring each phase is fully homogenous before combining can prevent issues.

Suggestions to Resolve the Issue

1. Improve Essential Oil Incorporation:

   • The most effective way to incorporate essential oil without heat is to use a suitable solubilizer. A solubilizer helps disperse the oil evenly in the water phase. Common solubilizers for essential oils in aqueous systems include ingredients like PEG-40 Hydrogenated Castor Oil or Polysorbate 20. You would typically mix the essential oil with the solubilizer first before adding this mixture to the rest of the formula.
   • Alternatively, if you are open to using gentle heat, warming the water phase slightly (e.g., to 40-50°C) can help with the dispersion of ingredients, including the essential oil (when added with surfactants).

2. Ensure Complete Xanthan Gum Hydration:

   • Make sure the Xanthan Gum is thoroughly pre-dispersed in the Glycerin (Phase D) until no dry clumps remain before adding this mixture to the water phase (Phase C).
   • Mix the water phase vigorously while slowly adding the Glycerin/Xanthan Gum mixture to ensure the gum hydrates evenly without clumping. Continue mixing until the gel is completely smooth and clear (if using the clear type) or uniformly thickened.

3. Review Mixing Procedure:

   • Ensure each phase (A, B, C, D, E) is fully mixed and homogenous before combining them according to your formulation steps.
   • Add phases slowly with continuous mixing to allow ingredients to integrate properly.

By addressing the solubility of the essential oil and ensuring proper hydration of the Xanthan Gum, you should be able to improve the stability and clarity of your shampoo formulation and prevent sedimentation.