Toner Precipitation Issue

Based on the ingredients in your toner formula and the issue of precipitation, the most likely cause is related to the solubility or stability of one or more ingredients in the final solution, particularly concerning the pH.

Looking at the properties of the ingredients you used:

• Japanese Cedar (Cryptomeria Japonica Bud Extract): The description for this ingredient states that it should be dispersed in water with a pH in the range of 3.5-6.5.
• Prebio-care (Skin Prebiotic): This ingredient is soluble in water, and the formula should have a pH range of 4-10.
• Dimethyl Isosorbide, Hexapeptide-9, and Probio-Protect: These are described as soluble or dispersible in water, with no specific narrow pH range mentioned in their descriptions as a requirement for solubility.

Given that Japanese Cedar extract has a relatively narrow required pH range (3.5-6.5) compared to Prebio-care (4-10) and the general solubility of the other ingredients, it is highly probable that the final pH of your toner formula falls outside the optimal range for the Japanese Cedar extract, causing it to precipitate out of the solution over time.

The precipitate you are seeing is likely the Japanese Cedar extract that is not remaining dissolved or dispersed at the pH of your formula. Shaking helps to temporarily disperse it, but it settles again because it is not truly stable under those conditions.

Recommendation:

1. Check the pH: Measure the pH of your finished toner formula.
2. Adjust the pH: If the pH is outside the 3.5-6.5 range, carefully adjust it using a suitable cosmetic-grade pH adjuster (like a dilute acid or base solution) until it falls within this range. This should help the Japanese Cedar extract remain properly dissolved or dispersed.

Ensuring the pH is within the recommended range for all ingredients is crucial for the stability and clarity of your formulation.