1/2 gallon apple cider, preferably organic and definitely preservative-free
1 gallon jar
cloth to cover the top.
Put the cider into the jar, and cover with the cloth. Set in a cool, dark place for a month or two. The trick to cider vinegar is that it needs oxygen for its fermentation process: you should make sure to stir it well at least once a day, replacing the cloth cover each time to prevent fruit flies from infesting...
This isn't suitable for canning, because you can't tell the exact acidity. But you can start eating it as soon is it passes through the alcoholic stage into vinegar-ness...
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