This is the my first attempt so no fancy tool here. All we need is some grapes, a blender, a large pot, a new/clean panty hose, or a large fine/med sieve or a cheesecloth or a piece of fabric/clean old sheet, etc. One pound of grape (3 cups) will yield about a cup of juice.
Put grapes in a large bowl, cover with water. Rinse and pick a small branch/bundle up at a time. Pull the grapes away from the stem. Discard the green and shriveled ones.
Raw fresh grape juice: use a blender on “Pulse” to mash grapes in a few minutes-to break the seeds loose and relieve the juice and liquefy pulp but keep the seeds whole. When the pulp just start to look smooth, stop and pour the grape mixture into a sieve or a food drainer of your choice. I cut a panty hose leg in two haft. Tie a knot at a loose end, stretch the opened end over the blender and empty the container into the pantyhose over large pot. The fresh raw grape juice has lighter pink color than the one cooked. The 100% grape juice is ready to drink and or store in the fridge. It is good few day.
Cooked grape juice: mash grape by a blender as above or potato masher or hand ( protect the hands with a plastic bag or glove from grape color) . Bring it to a boil, stir occasionally over medium high heat. Then lower the heat to simmer for 10 minutes without cover. Let it cool down to room temperature if use panty hose to strain the juice. Stretch the opened end of 1/2 panty hose leg over a medium/large bowl. Ladle cooked grape mixture over the panty hose.and start to squeeze the hose gently from the top to bottom. If using a sieve/cheesecloth, the hot mixture can be strained right away and when the mixture cools down, transfer the strainer to the fridge and let the juice dripping overnight. The juice will be clearer.
After sitting overnight in the fridge, some sedimen will appear at the bottom and floating around the sides of container. If you want clearer juice, strain the juice one more time to filter those sediment out.