"The house we bought has two unidentified grape vines on an arbor, loaded with grapes that ripen bluish-purple in big
bunches. Do you have a recipe that will produce halfway decent wine from such grapes?" similar requests from various requestors
Most of the requests of this nature have the following characteristics" (1) The grapes ripen in medium-sized bunches (2) of bluish-purple to purplish-black grapes (3) of decent size (4) in late August to mid-September (depending on location). The vines (5) are usually on an arbor or trellis structure, (6) were definitely planted by someone, (7) were untrimmed when the current owner acquired them, (8) exhibited vigorous growth after being pruned, (9) are winter hardy even in the Great Lakes regions, and (10) no one has a clue as to what kind of grapes they might be. Finally, (11) the grapes are very sweet and (12) good to eat. If you have similar grapes, this recipe is for you.
Unless there are other descriptors that would indicate another type of grape, I assume they are Concord grapes or a hybrid of Concord, as this is by far the most common yard grape in America. The Concord grape was first cultivated in 1849 and introduced to the market in 1853 by Ephraim Wales Bull of Concord, Massachusetts, Virtually everyone in America has tasted this grape, as it is the "red" grape that Thomas Bramwell Welch made famous in juice, jelly and soda. It has a distinct flavor, grows well almost everywhere, and is resistent to most (but not all) diseases that affect European grapes.
Your grapes may not be Concord. Generally, this recipe will work for most cultivated grapes, but the quality of wine will differ if the variety is another grape. By "cultivated," I mean a grape other than a wild native grape that was planted in a yard.
This recipe differs from most of my recipes because it begins with the pressed juice of the grapes rather than the grapes themselves. About 12 pounds of grapes will usually suffice to produce the amount of juice required, but this could vary by 1-3 pounds (especially if pressing by hand). Wash and destem the grapes, cull out any unripe or unsound ones, crush them by hand or with the flat bottom of a wine bottle, transfer them to a nylon straining bag, and either squeeze out the juice by hand or use a grape or fruit press to extract the juice. Alternatively, the juice can be steam-extracted or extracted with a juicer, although be wary of juicers that grind away at the seeds as this will produce a bitter wine.
If topping up with water, this recipe makes a wine with 12% alcohol by volume. If topping up with finished red wine, only adjust starting specific gravity to 1.088. Most people like this wine best with a little sweetness, but it also makes a very good dry wine.
Check specific gravity of juice and adjust to 1.088 by adding sugar (if too low) or water (if too high) or additional juice (if just right). Put juice in primary. Add Campden tablet (finely crushed and dissolved in some of the juice), cover primary with sanitized cloth, and set aside for 10-12 hours. Add pectic enzyme, recover the primary, and set aside another 8- 10 hours. Stir in yeast nutrient and add activated yeast. Recover primary. When specific gravity drops to 1.015 or lower, transfer to secondary fermentation vessel and attach airlock. Wait until all fermentation ceases and airlock is still for two weeks, then rack into clean secondary, top up and refit airlock. Wait additional 4-6 weeks and add another finely crushed and dissolved Campden tablet and 1/2 teaspoon potassium sorbate to clean secondary, rack wine onto it, top up and refit airlock. Wait 30 days, sweeten to taste, and bottle. Wait two months before tasting. [Author's own recipe.]
My thanks to all who have requested such a recipe.