1 cup leftover wine, white or red
3 tbsp good quality white or red vinegar that has the a bit of the gelatinous film floating on the bottom of the bottle (this is the starter)
1. Pour your leftover wine into a container with a large surface area, such as a bowl or wide-mouthed jar.
2. Add starter vinegar. Stir well.
3. Cover with a towel and let it sit at room temperature, stirring daily, until a thin gelatinous film starts to form on the surface. That will form into the mother. You will probably see it form 7-10 days after you begin the process.
4. Once it tastes more like vinegar and less like wine, move it to an airtight container, with very little surface area exposed. Although air is critical to the process of vinegar fermentation, continued exposure to air once you have your vinegar is a good way to ruin it/make it not be vinegar any more.