1.https://pubchem.ncbi.nlm.nih.gov/compound/glycerol#section=TasteThey should have taken you up on that bet. Making your own fog juice is definitely cheaper, and definitely dangerous. Store bought fog juice is made form near pharmaceutical grade chemicals, it's specifically blended to burn at fogger temperatures. One of the chemicals released if things go wrong is formaldehide (a colorless, toxic, potentially carcinogenic, water-soluble gas). I'd hazzard a guess, that if it the home made stuff seems to produce more fog than the store bought, it's because the home brew isn't mixed in the proper proportions, probably too much glycerine. It's just not worth the risk of poisoning yourself or TOTers. This topic gets brought up on every forum sooner or later, it goes hand in hand with the make your own fogger theory.