I was thinking along the same lines as Natch. I grew up helping my mother can things from the garden. And, I've continued to can vegetables, soups and things as a grown man. Because of the differing amount of atmospheric pressure found at different elevations, all good canning books say to process at a certain pressure for a certain amount of time if you are below a certain elevation. Then, it will tell you that if you are above a certain elevation, you should increase the pressure or processing time by "X" amount.
To me, it would stand to reason that extra pressure or processing time is added for higher elevations so that a higher vacuum is created inside the jar, thereby making it less susceptible to loosing its seal under the lesser atmospheric pressure at the higher elevation. It would also seem reasonable to me to assume that the seal that is used on tobacco tins is not of as high quality as those used on canning jars. Plus, it is extremely doubtful to me that the vacuum inside the tin ever comes close to reaching the vacuum inside a canning jar that has been properly processed. Therefore, I would have to conclude that tobacco tins that were sealed at a lower elevation would definitely leak once exposed to a higher elevation for any length of time due to the significant decrease in the outside pressure that helps maintain the integrity of the seal... unless one does something to improve or protect the integrity of the seal.
Gandalf, by adding wax to the tin's seal, you are doing just that... improving and protecting the integrity of the seal. So, unless you begin buying tobacco that was packaged and stored at an elevation similar to yours, I would think you would do well to continue to add the wax to the seal!
I wish it were convenient for you to go from where you are to an elevation that was at least 3,000 feet less than yours, then back to your elevation. If it were convenient for you to do that, you could try an experiment that might prove mine and Natch's theory.
Using a container that was preferably made of glass (to prevent atmospheric pressure change from being absorbed by container's softer sides... ie. plastic), you would use water to fill it brimming full while at the lower elevation. You would then screw the lid on; but not very tight... just tight enough to prevent any water from leaking if you were to turn the container over. You would then make sure the lid and outside of the container was completely dry.
Since toilet paper quickly absorbs and shows signs of any moisture, wrap the container in a layer or two of toilet paper. Then, transport the container back to your elevation. Then, check the toilet paper for any signs where the water may have leaked from inside the container. If you discover moisture or dampness on the toilet paper... Natch and I are right. If there is never any sign that water leaked from the container, I have just wasted the crap out of my time and yours!!!
:lol: But, I'd bet you'd discover that the container will leak once it is transported to the higher elevation!!
I don't know enough about physics to know what the difference would be between water leaking from a container and air leaking from the same container. But, knowing that it is easier to move air than it is to move water, I would also be willing to wager that the amount of air leakage from a container would be far greater than the amount of water that would leak from the same container under the same conditions.
I hope this made sense!! And, I hope it helps!!!
Robert
