FWIW, when I hear of thick residues, with commercial juices, my worry is that 1) they flavor for profit, with no regard for the fact we know nothing of the inhalation toxicity of food flavorings. And it's a matter of amounts. It's one thing to be inhaling 1% acetone, and another to be inhaling 30%.
The flavorings we DO know about lead me to worry #2. 2) The use of diketones. The thick buttery taste we love so much in our food. The Vanilla custards. The buttery cakes. Buttered caramel popcorn. Without diketones it's
impossible to make some flavors. And inhaling diketones causes obliteration of the fine bronchioles in the lungs. Irreversibly. At low inhaled amounts it's likely to not be devastating, but if people are using 30% flavoring, with flavors that contain diketones like diacetyl, they're being foolish. And from talking to the
juice vendors I get the distinct impression they don't want to deal with it, because they cannot make their best-selling "rich juices" without diketones.
So I just don't
vape commercial juices, it's cheaper anyway, and in my own liquids I avoid flavor types likely to contain diketones (no matter what they say), and I try to use a minimum of ALL flavoring, say 5% as a general limit. Less for some of the Chinese alcohol-based super-flavors.
