Thickness--> 1) reduce the temperature; 2) evaporate or heat some of the water off; 3) put more 100% caustic soda into the solution to increase the concentration and thickness: Since this stuff solidifies at 12o C, changes in it's physical properties are going to happen quickly.
GEL--> Don't know the answer for that. Never heard of anyone wanting to have it as a gel. Usually its the other way around. Liquid Caustic Soda is used to provide more of a uniform concentration throughout the mix. Gel will not do that.
Not enough can be said about the dangers of working with Caustic Soda. For example, if you were to get some in your eyes, at almost any concentration, it will "burn" your eyes. It does this by dissolving the eye ball! That is irreversible.
Good Luck, Old Salt
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