Color Stability Issue in Gel Formulation

The color change from reddish-brown to green in your water-soluble color mixed in a gel base suggests a stability problem. This can often be caused by several factors:

• pH Level: Many water-soluble colors are sensitive to pH changes. The pH of your gel base might be causing the color to shift over time. Check the pH of your gel and the recommended stable pH range for the specific water-soluble color(s) you are using.
• Interaction with other ingredients: Some ingredients in the gel base might react with the colorants, leading to a color change.
• Oxidation: Exposure to air can sometimes cause certain colors to oxidize and change hue.

To help stabilize the color, consider the following:

1. Check and Adjust pH: Ensure the pH of your gel is within the optimal range for the colorants used. You might need to use a buffer system to maintain a stable pH.
2. Proper Preservation: Ensure your gel is adequately preserved to prevent microbial growth, which can sometimes affect color stability.
3. Consider Chelating Agents: If metal ions are present in your water or other ingredients, they can sometimes interact with colors. A chelating agent might help.

Unfortunately, without knowing the specific water-soluble colorants and the exact composition of your gel base, it is difficult to pinpoint the exact cause and recommend a specific additive. However, focusing on pH stability and proper preservation are good starting points.