Brian Mailman wrote:

> It's my understanding that those who make wine vinegar do so on a
> continuous basis--that is, they just draw off a pint or so of what they
> need, boil and filter it, but they're constantly replenishing the
> barrel/cask with leftovers from this and that.
>
> B/

Thank you for your reply.
Here is the recipe: Aceto di vino, from Giulliano Bugialli's "Foods of
Naples and Campania"

2 slices white bread, crusts removed
4 cups dry red wine

Put the bread in a glass jar, then pour the wine over it. Place a piece
of cheesecloth over the top of the jar and set the jar aside in a
cabinet or on a countertop away from direct sunlight.

Let the jar rest for about 25 days. in this period of time the bread
will turn very dark in color and become almost gelatinous. This is the
so called mother of the wine vinegar. Carefully drain and filter the
wine that has become vinegar into a bowl., then pour into a bottle. The
vinegar is now ready to be used.

You can add more wine to the jar containing the mother of the vinegar.
This time the process of changing the wine into vinegar will be much
faster, about 1 week.