What is propylene glycol? Is it evil?
Mostly a topic found in the late 90s and early 00s, "PG" was heavily discussed in ASP. Some thought it evil, others benign. Eventually, it simply was understood. Here are some of the fruits of the discussion.
PG is propylene glycol. It is a humectant used to preserve moisture content in variety of things, from food stuffs to tobacco. It is considered safe for human consumption by the FDA and its use IS quite prevalent in modern society. In tobacco, specifically, it is added to maintain moisture and retard mold development. When used in very small quantities, it is hardly detectable. However, if used with a heavy hand it just plain tastes bad. It exists and is actually in most of the tobaccos we smoke.
Jeff Folloder, 2000-07-02
Propylene glycol and other humectants are heavily used in drugstore tobaccos and jar blends to keep them from drying out. Some of these tobaccos will not dry out if left loose on a newspaper for a week. Premium blends, however, usually do not have as much PG as drugstore blends, but it's hard to find one that has [absolutely] none. [...] Proplylene glycol can prevent tobacco from drying out and helps retard mold growth. It is, however, a chemical that many of us would rather not have in their tobacco. Discovering that a favorite blend has a small amount of PG in it is not going to keep me from buying it. But knowing that a blend is treated with PG and other chemicals might very well keep me from even trying it.
Bill Burney, 2004-01-03
Propylene glycol, used as a humectant and a preservative to extend the shelf life of tobacco and as a carrier for flavorings added to pipe tobacco, is deleterious in several respects. The abundant hydrogen in the molecule combines with oxygen very readily, inducing higher-temperature combustion and production of greater quantities of water, both of which adversely affect smoking properties. The stuff also is sweetish, but with an off-taste that some find quite disagreeable. Whether the overall effect in this realm is a benefit or a detriment is a matter of taste. My personal opinion is that use as a humectant is both unnecessary and deleterious to the smoking qualities of the tobacco, and it should never be used for this purpose.
James Beard, 2000-07-02
PG can be added by the retailer to the finished bulk product, or by the blender, or the grower, or the processor, or the warehouser, or anywhere in between, and in variable quantities. So yes, PG will be found in nearly every pipe tobacco blend available, and for most of us it ain't necessarily a bad thing.
Fred Latchaw, 2001-12-12
Propyline glycol is not the evil chemical that some believe it to be, but, like anything else, it can be abused, and often is in "cheap" tobaccos. Glycerin, glycerol and alcohol were widely used in the past in flavoring tobaccos. Why so much of the industry switched to PG is a question that can PROBABLY be answered by economics.
In a relatively pure state, PG is viscous, and somewhat slimy to the touch. It binds readily with water, and is often used in humidifying units in cigar humidors to maintain a fairly constant relative humidity of about 70%, considered ideal by many. It has a distinctive sweet taste and substatially lower toxicity than ethylene- and diethylene glycols, but high ingested doses have correlated with hepatic and renal diseases. Don't drink it. If your tobacco is sticky, and it won't dry out, you've probably got a good dose of PG present. It's also found in oil-free salad dressings, and a lot of cosmetics.
And, no, I don't use it, though tested samples of some ingredient leaf have shown small amounts present.
GL Pease, 2001-12-14
PG, or propylene glycol is a viscous, oily liquid that is a common additive in food stuffs and tobacco. It is hygroscopic in that it has a tendancy to "exist" at approximately 70% relative humidity. When combined with plain old ordinary water and held in suspension in, say, oasis foam, a realtively stable humidistat is formed. When the relative humidity drops below 70%, the water bond is "broken" and the water is "released" into the surrounding environment. When the humidity level rises above 70% water is absorbed from the environment and bound to the PG.
Tobacco can act as the lattice that holds the PG solution. A little bit of PG is not really capable of holding 70%, but it is capable of locking in some moisture. From a manufacturer's point of view, this can help perpetuate the integrity of a product that may wind up sitting in warehouse, transit, or on a shelf for an indeterminate period of time. Kudos to the manufacturer who does their best to insure that you get a properly moisturized, consistent product every time.
PG is also used as a flavor carrier. Since the PG will draw in moisture from the surrounding environment, many manufacturers will flavor tobaccos using PG as a "carrier". A flavoring agent is combined with water or other solution and then combined with an amount of PG. The subsequent solution is then combined with dry tobacco and the result is that the flavor is drawn into the tobacco mixture as opposed to just being sprayed or poured on.
Jeff Folloder, 2000-08-26
