4 ~ How well do vacuum-sealed plastic bags work for long-term storage? Why are vacuum-sealed tins different?
Now this... this has been the subject of much experimentation and debate over the years. Recently, debate has subsided more often in strong favor of the "aging needs air" contingent. Nevertheless, there remains a contingent of people who still have all that vacuum seal equipment laying around and use it to seal up their bulk. They seem to find it beneficial.
Fully evacuated plastic pouches: Up until about two years, these work fine at sealing the tobacco. However, minimal aging takes place, probably due to the lack of oxygen. The pressure compacts the mass into a fairly firm block, nothing like a real pressed flake, but pretty solid as the pressure continues over a period of years. I found the apparent effects of this "pressing" the best aspects of the method of storage. Unfortunately, somewhere between two and three years, enough H2O vapor escapes to begin a drying process, usually noticable around the edges of the tobacco mass, which begin to feel crispy through the plastic. Note that the vacuum remains tight--the plastic used apparently passes H2O more easily than O2, N2, or other atmospheric gasses. Bottom line: not recommended if you want to age the tobacco. I recommend double bagging and double sealing.
Toren Smith, 2001-07-25
No problems, just less real aging. Some air is necessary to start the whole process off. It's been shown that sucking out the air will "preserve" the tobacco in its current state, and that little or no change will take place over time. So, while it may be fine for storage, it's not going to provide the advantages of age. Toren's experiments, interestingly, also demonstrated that vacuum sealed tobacco can dry out, while still maintaining the seal! Apparently, the plastic used in the vacuum sealers is somewhat permeable to H2O, but less so to atmospheric gasses. Different materials provide a good barrier to different types of molecules, while being permeable to others. Not knowing what material the bags are made from, I can't comment on why this happened, but Toren's experimental methods are quite sound.
GL Pease, 2001-08-16 (revised 2003-12-23)
Vacuum sealing is a bad idea. (I read an ancient Rattray's catalogue on tobacco, in which was presented a short discourse by Charles himself. Old Chuck had some pretty strong words to say against vacuum packing, and experiments conducted by myself and others, notably Toren Smith's recently published findings, bear this out.)
GL Pease, 2001-08-15
There is a difference between an air tight tin and a vacuum sealed bag with all the air evacuated out. A sealed tin still has a small amount of air left in it. This allows the tobacco to age; the chemical reactions that take place in aging require some air to get going. A plastic bag with all the air removed will not have enough air left for the reactions to start.
Mark Hogan, 2003-05-21
The vacuum used to seal tins is minimal. Foodsaver type vacuum pumps are quite weak, but they do a very good job of evacuating a great deal of the air from the bags they use [which therefore prevents substantial aging from occuring].
GL Pease, 2003-07-06
None other than Charles Rattray himself first wrote, in his "Disquisition for the Connoisseur" that vacuum sealing tins is NOT ideal. Prior to the more recently common flat tins, such great old brands as Balkan Sobranie, Rattray, McConnell, Drucquer & Sons, and many others were put in tins similar to what we use today. All the old knife-lid tins were sealed at normal atmospheric pressure, not vacuum packed. Still today, quite a few producers continue with the "old school" method of atmospheric sealing. Vacuum sealing is the new fangled method that is done by producers who rely on assembly line techniques to speed production and reduce costs.
I've explored the virtues of aged tobaccos throughout my 25 years as a pipe smoker, having been introduced to aged tobacos by Robert Rex during my pipe smoking infancy. While many wonderful experiences have come from well-aged tobaccos vacuum-sealed in hockey puck tins, the most memorable have always come from the old-time, "conventional" containers. Vacuum sealing is certainly not necessary, and I'll stick to the notion that it is not ideal. After all, who am I to argue with Chas?
GL Pease, 2005-04-18 on Knox Cigar Boards
Vacuum sealing, while quite popular, is simply a waste of time, and may actually be detrimental to the overall aging potential of the tobacco. Certainly the plastic materials that are used with home-vacuum sealers are NOT high-barrier films, and while they'll keep most of the water in, they'll let much of the goodness out.
GL Pease, 2005-08-20