I bought a house that happens to have a grape vine producing lots of fruit. They are quite small (approx 12mm diameter) and not very sweet, but black in colour. I do not know the varietal.
Can anyone tell me if its worth trying to make wine out of them? All the "make your own wine" guides seem to omit statements about general suitably of the source fruit.
leaves:
First let me say you can pretty much make wine from all grapes, just some of that wine will be better than others.
If I had a picture of the leaves, I could probably tell if it's wine grapes or not, but I am guessing that it's just table grapes. I think the easiest way to guess that wine grapes get powdery mildew quite easily and table grapes (bred from north American grapes vs. European grapes for wine grapes) don't get powdery mildew. Here is a good website showing what it looks like on grapes. If they are wine grapes, they should have it by now (unless you have been spraying chemicals to prevent or get rid of it).
The other key indicator you won't be able to figure out until the grapes fully ripen. When they are ripe, squeeze the grape and if the skin slips off the inner part of the grape, then they are table grapes. If the skin just spits and juice comes out, wine grapes.
I'm about 99% sure you have a table grape since that's what most people outside of wine growing regions have access to and they are much more rugged than wine grapes. My bet is that you have a Concord, which is the most common backyard grape in the USA.
Yes, you can make wine from them. You might have to add some sugar since table grapes don't get as sweet as wine grapes, but it should make a decent wine!
If they are not sweet, they are most probably not very good to make wine. Some grapes are good to be eaten, but do not produce good wine.
I tried making wine from sweet dark grapes that looked like wine grapes but were not (forgot the name), so I ended up throwing it out, the lack of acidity and taste were not up to par.
You can try a small quantity, add sugar if the grapes are not sweet enough. If you find the result good enough, you may buy some wine grapes and mix them together next time.
It's worth trying.
Wine grapes have a really thick pith inside and make seeds, table grapes generally have less pith and are seedless varieties. Here's a diagram. Harvesting them when ripe is the hard part, you have to take a random sample and check the sugar levels with refractometer. Iirc, 31 brix or so is fully ripe; less suitable varieties will peak at lower values.
Edit: Here are the exact parameters for wine grape harvest that would make good wine: "Brix: >24 ; TotalAcid .58 - .65 ; PH 3.4 – 3.6" from source.
