Making balsamic vinegar requires boiling Trebbiano grapes until they are reduced to a syrup, adding a vinegar culture and then aging the syrup for about 10 years. As true champagne is made in the Champagne region of France, true balsamic vinegar is made in the Modena province of Italy.
Although it is labeled as a vinegar, balsamic vinegar is made using a different process than most vinegars. Most vinegar is simply wine that is allowed to sour. It is easy to make wine vinegar at home by adding a culture and a bottle of wine to a container, covering the container with a cloth and then placing it in a cool, dry location. Every week or so, the wine should be topped off. In about three months, the transition of the wine to red wine vinegar is complete.
However, balsamic vinegar is not made from wine. Rather, it is made by reducing grapes to a syrup, allowing the syrup to age into a wine and then allowing the wine to age into balsamic. This process takes years, so homemade versions of true balsamic vinegar are very difficult. The longer balsamic vinegar is allowed to age, the more flavorful it is. Some balsamic vinegars are aged more than 100 years.