Evaluation of Your Hair Spray Formula

Thank you for sharing your hair spray formula idea! It's great that you're combining ingredients known for their potential benefits for hair nourishment and reducing hair loss, like Rosemary Water and Melatonin. Let's evaluate your proposed formula:

• Rosemary Water (60%): This is a good base for a hair spray and is traditionally used for scalp health. At 60%, the preservative already present in the Rosemary Water should help preserve the water phase.
• Olive Oil Water (Olive Oil PEG-7 Esters) (4%): This water-soluble emollient is a good addition to provide some light moisturizing benefits without making the spray feel greasy. The concentration is within the recommended range.
• Pure-Melatonin (2%): Melatonin is interesting for hair loss, with research suggesting effectiveness at concentrations as low as 0.1%. Your proposed 2% is within the allowed range (0.1-3%), but it's a relatively high concentration. While it might offer enhanced benefits, it also presents formulation challenges.
• Water (34%): This makes up the rest of the water phase.

Compatibility and Formulation Considerations:

1. Melatonin Solubility: Pure-Melatonin powder is not directly water-soluble. It dissolves in certain oils and glycols (like Ethoxydiglycol or 1,3-Propanediol). Mixing 2% directly into your high-water formula (94% water phase) will likely result in undissolved particles or instability. You will need to dissolve the Melatonin in a suitable co-solvent (like a small amount of 1,3-Propanediol) first before adding it to the water phase.
2. Melatonin Stability: Melatonin is sensitive to air, heat, and light. A standard spray bottle might expose the formula to air over time, potentially degrading the Melatonin. For better stability, consider using an airless pump bottle or an opaque/dark bottle and store the product in a cool, dark place.
3. pH Level: Melatonin requires a pH between 4 and 10 for stability. You should check the pH of your final formula and adjust it if necessary to be within this range.
4. Preservation: While the Rosemary Water contains a preservative, adding other ingredients and water means you should ensure the overall preservative system is robust enough for the entire formula and intended use (spraying onto the scalp). You might need to add a broad-spectrum preservative blend.

Regarding the Smell:

Rosemary Water has a natural, distinct herbal scent from its volatile oils. Olive Oil PEG-7 Esters and Pure-Melatonin are generally odorless. Therefore, the dominant scent of your spray will be from the Rosemary Water. If you find this scent too strong or undesirable, you could try adding a small amount of a cosmetic-grade fragrance suitable for hair products. However, adding fragrance can sometimes cause irritation, especially on the scalp.

Overall Feasibility:

The concept is good, combining beneficial ingredients. The formula is feasible but requires careful attention to dissolving the Melatonin using a co-solvent and ensuring its stability through appropriate packaging and storage. Using a slightly lower concentration of Melatonin (e.g., 0.5% or 1%) might simplify the formulation while still providing benefits based on research.

Remember to perform stability testing on your final formula to ensure it remains stable and effective over time.