Explanation for Gel Melting

The gel you made using Ceteareth-25 likely melted because it was exposed to high temperatures inside the car parked in direct sunlight. Ceteareth-25 is a non-ionic emulsifier and thickener that creates a gel structure, but this structure can be sensitive to heat. When the temperature rises significantly, the gel matrix breaks down, causing it to revert to a liquid state.

It's not necessarily a mistake in your formulation process. The issue is the storage condition. Cosmetic products, especially gels, should be stored at room temperature and protected from direct sunlight and heat to maintain their stability and texture.

To prevent this from happening again, always store your finished gel product in a cool place, away from direct heat sources like a hot car or direct sun exposure.