Why the Gel Didn't Form

• Carbomer's Sensitivity: Carbomer 940, which you used, is sensitive to electrolytes (dissolved salts) and acidity. When water contains these impurities, it interferes with the Carbomer's ability to swell and form a gel structure after neutralization with an alkali.
• Water Purity: Distilled water from a reliable source, like the one you previously used from MySkinRecipes, is highly pure and contains minimal dissolved solids. Deionized water from other sources, especially from a gas station, may still contain significant levels of dissolved salts or other impurities that prevent the Carbomer from working correctly.
• Electrolyte Interference: The dissolved salts in the impure water act as electrolytes. These electrolytes disrupt the polymer chains of the Carbomer, preventing them from properly hydrating and cross-linking to form a stable gel network. This results in a liquid, unthickened mixture.

How to Check and Resolve

1. Check Water Purity: As suggested in the forum reply, you can use a TDS meter to measure the Total Dissolved Solids in the water. Water suitable for cosmetic formulations using sensitive thickeners like Carbomer 940 should ideally have a very low TDS reading (typically below 20 ppm).
2. Use Pure Water: Always use high-purity water, such as distilled water or properly deionized water from a trusted source, for formulations using Carbomer 940.
3. Consider Electrolyte-Tolerant Thickeners: If you need to use water that might contain some impurities or if your formula includes ingredients with electrolytes, consider using a gel maker that is tolerant to electrolytes. Examples include Pro Polymer, Carbomer Ultrez 30, or Carbomer 2020.

Using pure water is crucial for achieving the desired gel consistency with Carbomer 940.