Hair Treatment Viscosity Increase Over Time

This sounds like a stability issue with your hair treatment formulation, specifically related to rheology (viscosity) changes over time. An increase in viscosity after manufacturing can be caused by several factors.

Here are some potential reasons and things to check:

• Delayed Hydration or Swelling of Thickeners/Polymers: Some polymeric thickeners or gums may continue to hydrate or swell slowly over time after the initial mixing, leading to a gradual increase in viscosity. Ensure your manufacturing process allows for complete hydration of such ingredients during production.
• Ingredient Interactions: Interactions between different components in your formula (e.g., between thickeners, emulsifiers, electrolytes, active ingredients, or preservatives) can change the structure of the formulation matrix over time, causing viscosity to increase. This could be due to complex formation, cross-linking, or other chemical/physical interactions.
• pH Changes: The viscosity of many thickeners and rheology modifiers is highly dependent on pH. If the pH of your formulation is drifting over time (e.g., due to ingredient degradation or interaction with packaging), it could cause the viscosity to change.
• Temperature Fluctuations: Storage conditions can affect stability. Significant temperature variations might impact the physical state of the formulation and its viscosity.
• Microbial Activity: While less common for causing viscosity increase (usually causes thinning or separation), microbial contamination can sometimes alter the formulation's properties in unexpected ways. Ensure your preservative system is effective.

How to troubleshoot:

1. Review your formula: Look closely at your thickeners, polymers, emulsifiers, and any ingredients known to interact.
2. Check your manufacturing process: Ensure all ingredients are properly dispersed and hydrated according to supplier recommendations. Check mixing times, temperatures, and order of addition.
3. Monitor pH: Track the pH of your formulation over time to see if it's changing.
4. Stability Testing: Conduct accelerated stability testing (e.g., at elevated temperatures) and real-time stability testing to observe changes in viscosity, pH, appearance, and odor over time. This can help identify the rate and nature of the change.
5. Ingredient Quality: Ensure the quality and consistency of your raw materials.

Without knowing the specific ingredients in your formula, it's difficult to pinpoint the exact cause. You may need to systematically test variations of your formula or consult with a cosmetic chemist specializing in formulation stability.