It should work well, maybe even excellent.
I do the following:
1.) Wash the grapes.
2.) Pick them off the stems
3.) Add the grapes and a bit of water to the bottom of a very large pan
4.) Cook them until they soften.
5.) Mash them and cook a bit more.
6.) I strain it with a colander (gets most of seeds and skins) and then filter again with a sieve (smaller particles). You can just use a jelly bag for these last steps, but I’ve never gotten one.
7.) I repeated steps 1-6 with some white and red currants and mixed the result (you can substitute pectin, the normal way to make it gel, which you should be able to buy in the grocery store, possibly near the jello).
8.) Then heat the liquid up and mix sugar and pectin in.
9.) I use a frozen plate (keep it in freezer for a few minutes) to test when it is solid enough. If it isn’t solid enough, boil more.
10.) When solid enough, spoon it into jars. If you don’t use a canning method to prep the jars (I don’t) then you should store the jelly in the fridge, instead of at room temp.
This way works for me, and I’ve been making jelly/jam for a few years now. But, I’m still a newbie compared to a lot of the others on here (Mrs G, Drew, etc)- I’m sure that some others will have different methods.
Note- you can stop after Step 6 and use it as grape juice (sweeten if needed). My kids thought it was too sour if I just used the colander and skipped the fine mesh sieve step.
Thanks Bob. That’s quite a bit of work!
Would gelatin work like pectin? I think I have few boxes of gelatin but no pectin…
Tom
I do it pretty much the same way. Some notes. i add 1/2 cup lime or lemon juice to increase acid, helps in the gel, and also lowers pH so the botulism organism cannot grow. You can also add pectin by using apple juice, or even better grating an apple into the mix. If you don’t use pectin, i would do this if you do not have currants.
Tom this is an excellent recipe and the best way to keep your jams for six months is to use a canner.
Thank you Mrs.G for the link.
I’m just trying to save the un-wanted sour grapes so just dapple into this jam arena! I have no specialized canning equipment yet so it’s going to be cooked them up and redistribute to family members with instruction: Eat them within 2-3 weeks! 
I see that the epicurious site recipe uses no pectin, so the main process is to cook down all the extra liquid? Can I use an apple instead of lemon juice? And if thing did not gelling properly, can I use gelatin to get thing settle?
Tom
There are many ways to make jam. I always just cook it down until it sets. Grapes usually have enough natural pectin in them for a good set. I use a thin layer to shorten the cooking time. Put some spoons in the freezer and throw a tiny bit on the spoon to test for doneness - if its not jelling on the cold spoon it won’t gel in the jar.
Like Scott, I rarely use pectin. I’ve only used it for making sour cherry jam which is excellent. Canning materials are not that expensive. You grow a lot of fruit and enjoying it out of season is a real treat. A canner costs about $26.00. Most hardware stores carry all of the supplies you might need.
You can use applejuice to add pectin (natural in apples and currants) but for grape jam you don’t need it. 
Thanks Scott and Mrs.G for your advices.
Like swimming, I like to get myself a bit acclimated with the cold water before plunging into the pool so once I’m comfortable with this fruit preservation process, then I would think about canning supplies.
Last question, is there any chance that you might missed the fine tipping point or over-cooked while [quote=“scottfsmith, post:128, topic:2120”]
cook it down until it sets?
[/quote]
Tom
I did the grapes jam this evening but forgot to take some key photos! But here’s the finished product! I think it’s spreadable…
While cooked down the juice…
From 2.5lb down to 3 jars!
Congrats Tom!
Its a big challenge to gauge when to finish, I have missed it many times. My recent grape jam I pulled a touch too soon. Its one of those things that experience is very helpful for, the look of the jam while cooking changes in regular ways. As it gets toward the end it becomes more translucent and changes the form of the bubbles to keep little “pockmarks” when a bubble pops, making it look something like bubbling lava. First it clarifies, then the pockmarks start to show up, then its time to turn off the heat.
Your jam looks a bit underdone since its not looking too clear, but that could just be the picture. If it is indeed underdone, its sauce or syrup and is still delicious. Pour it on yogurt, waffles, into smoothies, etc.
Thanks Scott.
Do you mean underdone as not enough cook time? I thought the bubbles popped with viscosity like “bubbling lava” as you described. I was more concerned of burning it since it’s getting dense in texture. Nevertheless, I tried a spoonful with my wife, we both loved its taste. And my son franticly looked for a piece of bread to spread it on after he tasted it! Too bad that we ran out of bread this evening!
I just wonder if anyone ever put creative ingredient into this jam, say like vanilla, orange peel, basil, etc.?
Tom
The strong power of concord grape flavor will be over whelmed by almost any other flavor. Sometimes best is just best.
Right. The downside if you don’t cook enough is it is runny and runs off the toast.
That’s interesting.The way the directions that came with the pectin I used,made it seem like if the exact amount of sugar wasn’t used,the jam wasn’t going to set. Brady
I had one of the grape jelly batches not gel properly. After it sat for a few days in the fridge, I poured it back into the pan and boiled it for a while longer. After that, it had just the right consistency.
you need to do two things for pectin free jam; reduce the water and heat the sugar to almost soft ball stage (thicken), a candy thermometer isn’t a bad idea.
I think I had the new player’s luck. This morning, my grapes+1 apple jam set well from last night cooking and no pectin with some home made bread, not runny at all…
Way to go Tom! My first batch many years ago was sour cherry preserves, I burned the first half and the second was too runny.
@Bradybb , the commercial pectin boxes have a certain formula of a lot of sugar to get an easy set. I never follow that recipe myself as I find it too sweet. But for something low in pectin like sour cherries I may add 1/2 a box near the end to help induce a good set.
Also you can redo it. Just start over. Again why i like pectin, it’s very predicable and my jams now are always firm. You can buy it in bulk, so cost is not that much.
Yeah, that’s BS. Use the low sugar pink box pectin as a 2 to 1 ratio works.
I used to not use pectin, I stated reasons why I do now in other posts, another is time is money. You only need 15 minutes of prep. So it takes very little time.
I have never been able to get black raspberries to set without pectin.