Clean Grapes. Black Grapes has a kind of powdery covering. To clean it properly, wash grapes in running water 2-3 times.
Take water in a container add sea salt to it and soak grapes in it. Keep grapes for about 15-20 mins. Rub grapes lightly to remove the residue. Then drain the water, wash again one more time.
In a pan add 2-3 cups of water. Add washed grapes.
Boil grapes in water, till the peel starts to come out. Grapes will also change a bit of color.
Switch off the gas. Let the grape mixture cool completely.
Next drain the colored water and then transfer the grapes to a grinder/ blender.
Pulse 1-2 times. Do not grind to a smooth paste. The peels may not taste bitter and also you won't get a clear solution.
Alternatively, mash the grapes using a potato masher or better use you hand to take out pulp and separate the peels.
Strain the mixture again. Add about half cup water, if the mixture is too thick.
Finally when you take out all the pulp and are left with peels, take the clear mixture in saucepan/pan, add sugar/jaggery powder.
Boil the mixture for 5 mins. Take off the gas and cool completely.
Once cooled, add lemon juice and then fill and store in sterilized bottles.
To make large batches adjust the ingredients accordingly as per the quantity of grapes.