The first lamp had the all-too-common problem of the black leeching into the (originally) clear liquid, so red food coloring took care of that one. The second lamp had never cleared to my liking, and the wax was sluggish as well. For that one, I removed the liquid & saved it for another project. I replaced it with the purple liquid from an old purple/yellow with ridiculously foamy wax that had always looked like crap. Then, it took a whole lot of glycerine to finally get the wax moving, but I was ultimately successful.