This was posted some time back by the member Staffwalker (and reposted by Paul the Pipe Ninja if I remember correctly):
Here is the method I have used for years and have never had anything go wrong. Use Mason jars but they don't have to be new, use old ones if you have them and wash them thoroughly. The important thing is to use a NEW lid for each jar, they are very cheap and can be purchased at any grocery store. I always buy new rings also but you can use old ones provided they are free of rust and not bent and misshapen.
I run the jars, new or old, through the dish washer but you can wash by hand if you don't have a dish washer. (Use hot water as hot as your hands can stand, rinse well, soap makes tobacco taste bad). When the washer stops and before it has a chance to go into drying cycle, take the jars out and place on the counter-top, openings down, on a clean towel. There will be a little moisture left in the jars but it will be hot, sterilized, water from the dish washer. I don't dry them, preferring to put my tobacco up with a little moisture rather than too dry. When they are opened if the tobacco is too moist for your taste, leave it open for an hour or so, it will dry out to suit you.
Open a box of new lids, separate them and place in a sauce pan of water on the stove. The water should be just at the simmering point to soften the rubber seals. Be careful you don't allow it to boil because boiling water will melt the rubber.
Pick up a jar, fill with loose tobacco, (you can pack it rather tight or leave it loose, doesn't seem to matter much, in my opinion, although loose jars may seem to age a little more rapidly), place in the microwave for about 20-30 seconds WITHOUT the lid. (I wouldn't do more than 30 seconds, you don't want to cook the tobacco as it may change the taste. The purpose of this step is to heat the tobacco to insure a good seal when you place a lid on the jar. (As the heated air in the jar cools it will contract, pull the lid tight and seal the jar). Take it out of the microwave,check there are no flakes of tobacco between the lip of the jar and the rubber seal under the lid. and immediately place a new lid on the top of the jar and hand tighten a ring to hold it in place. Sit it aside and do another one. If you have heated the jar and tobacco correctly in about 10-15 minutes you will hear a pop as the lid seals. You can test each one by pressing in the center of the lid. If you press down and the lid center springs back it is not sealed. Let it sit overnight, in the morning if it hasn't sealed, reheat in microwave and use a new lid.
Once it is sealed, you are good to go, the tobacco will keep forever or until the lid rusts through in about 25 years. Do not, never, open a jar until you are ready to smoke it. If opened, the seal is lost. In a couple of weeks the rubber will have made a semi-permanent seal with the jar. At this point, you can leave the rings on or take them off for re-use.
I smoke a lot so I like to use pint jars but if you don't smoke so much use 1/2 pint jars. A pint jar lasts me a couple of weeks and never dries out as long as I replace the lid and tighten the ring down after I fill a pipe. bob gilbert
: