Add all of the grapes into a large tub. Fill it with water and allow the grapes to hang out in the water for five minutes. This will help to flush out any earwigs or bugs.
Remove all of the grapes from the stems (and any bits of broken off stem from the grapes). Spread the grapes in a single layer on dehydrator trays.
Dehydrate for 24 hours or according to your dehydrator's specific temperature and instructions. The homemade raisins should be soft, but not overly squishy. And not yet hard. Dehydrated fruit is all about finding that balance. (I'm assuming you know what a raisin feels like. Dehydrate your homemade raisins until they feel like that). See how helpful I am?