Choose unripe, tight-skinned, preferably green seedless grapes harvested about 2 weeks before optimum eating quality. Stem, wash, and drain.
For hot pack, blanch grapes in boiling water for 30 seconds, drain, then pack as directed for raw pack.
Fill jars with grapes and hot syrup, leaving 1-inch headspace.
Process hot-pack pints or quarts 10/15/15/20 minutes at 0–1,000/1,001–3,000/3,001–6,000/above 6,000 ft. Raw-pack pints process 15/20/20/25 and quarts 20/25/30/35 minutes.