Chemicals similiar to "Freon" (Dupont's trade name for trichlorotriflouroethane) leave no residue.
In the case of LAST it's use was strictly as a carrier and had no efficacy of its' own. Much like solvent or water in paint, it served as a vehicle to carry the active ingredient(s).
In any case, there are other chemicals that have replaced halogentated (i.e. chlorine, flourine, and bromine based) products so there should be no difference in performance in LAST which is a useless product by any standard.
In the case of LAST it's use was strictly as a carrier and had no efficacy of its' own. Much like solvent or water in paint, it served as a vehicle to carry the active ingredient(s).
In any case, there are other chemicals that have replaced halogentated (i.e. chlorine, flourine, and bromine based) products so there should be no difference in performance in LAST which is a useless product by any standard.