| jon ee-- You're actually talking about two difference processes here. Indeed, putting non-pastuerized cider in a barrel will eventually ferment. It's a little more technical than that if you want something that's consistently drinkable, since there are issues like sufficient sugar content, acid levels, avoiding acetobactor contamination that will affect how good the final cider is. The second process is called fractional distillation and it is how New Englanders made Apple Jack (also called "Frozen Heart" some places.) Most fermented cider (unless there's been lots of sugar added) will ferment out at somewhere between 4-6% ABV. Now, since alcohol has a lower freezing termperature than water, if you put the cider out in the cold, the water will freeze, but the alcohol won't. If you continue to remove the water, the alcohol will eventually get concentrated. It is possible, in really cold places, to get a liquid that's as high as 40 proof. There is a problem with this, however. Actually several. It's illegal. Secondly, whereas a still tends to purify the alcohol content, the freezing method tends to concentrate the alcohol along with the impurities. Ethers. Aldehydes. Fusel oils. Ironically, the part that gets purified is the water, which is skimmed off. Applejack, therefore, has a long and storied reputation for providing a roaring buzz and an even more roaring hangover. Worse, there have been many reported cases of apple palsy over the years, probably from ingesting all those occasionally nasty hydrocarbons compounds. So, that's probably more than you wanted to know. One more note: these days most amateur cidermakers use glass or plastic fermentation vessels. Barrels are very high maintenence and are a lot of work to keep clean and sweet. If you don't, you may end up with 50 gallons of salad dressing. Don | 
