Liquid glycerin can be turned into a solid by cooling it below its melting point. To do this, you can place the liquid glycerin in the refrigerator or freezer until it reaches a solid state. If you need to solidify it quickly, you can also mix it with an equal amount of water, which will cause the glycerin to form a gel-like consistency. Once the mixture has reached a gel-like consistency, you can place it in the refrigerator or freezer until it is solid.