Start Your Dehydrator based on the temperature your brand recommends. I'm using an Excalibur Dehydrator today. It recommends (135°F) = (57°C) degrees.

Wash, and remove the grapes from the stems. Discard any damaged ones.

Slice in half, if desired. If you don’t slice the grapes they will take longer to dehydrate.

Place the CUT side up so they will dry more evenly. Leave space between the grapes for the air to circulate.

Fill your trays and let them dehydrate naturally.

Most grapes will take between 18-48 hours. I dried them until they were wrinkled and pliable. They took about 48 hours. (They were the largest grapes I have ever dehydrated) The time will vary depending on the humidity of the room or area where you are drying the grapes.

If you live where it’s HUMID: “To condition the fruit, take the dried fruit that has cooled and pack it loosely in plastic or glass jars. Seal the containers and let them stand for 7 to 10 days. The excess moisture in some pieces will be absorbed by the drier pieces. Shake the jars daily to separate the pieces and check the moisture condensation.” https://nchfp.uga.edu/how/dry/pack_store.html

I used to live in the DRY DESERT: I set my fruit and vegetables on my countertop for 5-7 days. Ten days is even better to make sure everything is dry before using your FoodSaver unit.