In a large non-reactive saucepan, crush the blueberries with a potato masher or back of a large spoon. Stir in vinegar and sugar; bring to a boil and stir until sugar dissolves. Remove from heat and allow to cool.
Pour the mixture into 1-quart jar or storage container; cover and refrigerate 48 hours to allow flavors to blend.
In a fine wire sieve, strain blueberry mixture pressing out as much liquid as possible; discard solids. Line the sieve with cheesecloth and strain out finer particles. Pour vinegar into a glass bottle or jar and cover. Refrigerate.
Uses: vinaigrettes; marinades and glazes for red meat and game; barbecue sauces; beverages Yield: 1-1/2 cups