We've made this several times and it's sweet bland and horrible!
It's better to use tinned blackcurrants which make a much nicer wine!
Two tins Blackcurrants
250 ml grape concentrate
1 tsp pectolase
1 tsp acid blend or citric acid
Pour 4 pints of boiling water(two kettles full is about right) over the fruit and add the sugar.
When cool to room temperature add the rest of ingredients and 2 pints of cold water.
It should start bubbling within 24 hours. If it doesn't, add more yeast because you killed the first lot!
After 2 days strain off, use a coarse straining bag that you can buy off us. Or, improvise if you must with muslin or the net curtains.
Put into a clean demi john with an airlock and leave to ferment out. This may take a few days or a couple of weeks depending on the temperature.
When the bubbles stop coming through the airlock, or slow down to about one every 2 minutes test the wine.
Either use a hydrometer or taste it. If it's too sweet leave it longer.
If it's dry(sour taste) or just right syphon off into a clean demi john.
Add 1 campden tablet and potassium sorbate.
Leave to clear.
When clear, syphon into a clean demi john or bottle.
If it's too dry you can sweeten with sugar but keep a check that it doesn't start fermenting again. Leave it a couple of weeks then add a campden before bottling.