Sugar clogging atomizers seems very reasonable, especially considering how fragile some attys are. Still just to put things in perspective:
NAME___MELT(C)/BOIL(C)/TASTE/SMELL
L-Lactic Acid__53/122 /acid,sour/ none
Ethyl Lactate___-26/151/?/buttery,coconut
Ethyl Maltol___85/161/?/caramel,cooked fruit
D-Propylene Glycol___-59 /189/none/slightly sweet
L-Propylene Glycol___-59/189/none/slightly sweet
Xylitol___96/216/sweet/?
Nicotine___-79/247/bitter/sharp
Glycerine___18/290/slightly sweet/none
Keep in mind that some of these might interconvert in the presence/absence of water or at different ph levels, to different (but similar) compounds.
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Stevia and Steviol Glycosides failed my criteria as being too heavy and not having a boiling point below Glycerine (my cut off point), like most sugars. If you try to vape stevia extract have some extra attys around, and if your smoke starts to dwindle, I'd quit and clean the atty while you still can.
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Lastly if you read my post carefully you might get the idea that Acetoin and Diacetyl are both dangerous to vape. ONLY Diacetyl has been linked to lung damage. In fact, Acetoin is one of the less irritating inhalants at least according to the MSDS. Still there are no long term studies for any of these except for Propylene Glycol.