EasyThick™ Instability: Gel Collapse in Dishwashing Liquid After Adding Color and Fragrance
Question
EasyThick™ Instability in Dishwashing Liquid Formulation
I am formulating a dishwashing liquid using EasyThick™ (PEG-90 Glyceryl Isostearate) as the gelling agent.
The initial process successfully formed a thick gel. However, during the final step of adding liquid fragrance and food coloring, the gel instantly collapsed and turned back into a liquid.
- Is this instability caused by the food coloring or the liquid fragrance?
- What specific types of liquid fragrance and color are compatible with
EasyThick™to maintain viscosity?
- Note: When testing with HEC (Hydroxyethylcellulose) as the gelling agent, adding fragrance and color only resulted in a slight drop in viscosity, not a complete collapse, unlike the result with EasyThick™.*
Answer
The instability you are experiencing is a common issue when using EasyThick™ (PEG-90 Glyceryl Isostearate), which is a non-ionic, surfactant-based thickener that relies on forming a specific micellar structure with the detergents in your formula.
The instant collapse of the gel is almost certainly caused by one or both of the following:
- Food Coloring (High Electrolyte Content): Food-grade dyes often contain a high concentration of electrolytes (salts). High levels of electrolytes are known to instantly disrupt the micellar structure formed by surfactant-based thickeners like EasyThick™, leading to a complete and immediate loss of viscosity.
- Liquid Fragrance (Solvents/Solubilizers): The solvents or solubilizers used to make the liquid fragrance can interfere with the thickening mechanism. If the fragrance is not fully water-soluble or properly pre-solubilized, the oil phase can destabilize the entire system.
Recommendations for Compatible Ingredients
To maintain the viscosity provided by EasyThick™, you should use ingredients specifically designed for surfactant systems:
1. Coloring Agents
- Avoid Food Coloring: Stop using food coloring entirely.
- Use Cosmetic-Grade Dyes/Pigments: Switch to cosmetic-grade liquid dyes or pigments that are specifically formulated for use in shampoos and liquid soaps. These products are manufactured to have a much lower electrolyte content, ensuring stability in surfactant systems.
2. Fragrance Agents
- Use Pre-Solubilized Fragrances: Choose fragrances that are already formulated to be water-soluble or easily dispersible in liquid soap bases.
- Pre-Solubilize Oil-Based Fragrances: If you must use an oil-based fragrance, you must pre-mix it with a dedicated, compatible solubilizer (e.g., Polysorbate 20, PEG-40 Hydrogenated Castor Oil) at the correct ratio before adding the mixture to the main batch. This ensures the fragrance is properly incorporated and does not interfere with the thickening mechanism of EasyThick™.
Why HEC was more stable
Your observation that HEC (Hydroxyethylcellulose) only dropped slightly is correct. HEC is a polymer-based thickener (hydrocolloid) that thickens through hydration and entanglement, a mechanism that is much less sensitive to electrolytes than the micellar thickening mechanism of EasyThick™. This difference in thickening mechanism explains the drastic difference in stability when disruptive ingredients are added.
