I'm finally getting around to beginning to test this deep eutectic electrolyte. I mixed choline chloride with urea in a 1:2 mole ratio in a glass container. It formed a sludge. I sealed the container and then came back two days later to begin electrolysis and the mixture had formed a hard solid!
The whole time the mixture was at room temperature, and except for the mixing stage it was sealed.
So what am I missing? Is this a sign my reagents are bad? Or do these eutectics have a limited mixed life?
Update: Following Beerhunter's suggestion I ran the reagents in a blender until they formed a very liquid (low viscosity), homogenous mixture. But one day later the DES is crystallizing again at room temperature: