Over the last week and a half, we dried a batch of unknown-variety grapes we foraged from around town. We placed them on our house roof, on electric dehydrator trays, for about 5 days, then moved them onto screening in the solar dehydrator for a few more days after the weather turned mildly rainy.
Then we left the grapes in way too long, and they became super-dry raisins, with super-brittle stems. I started trying to pick the raisins out one by one, but found that took much longer than I wanted to devote to the project, as large pieces of stem broke off, attached to the raisins. I decided I didn't mind if I ate raisins with their immediate short stem attached, so long as I could separate out the rest of the grape bunch's stems. I found a method which seemed to work pretty quickly and efficiently.
Almost all the raisins had dried to such an extent that I could vigorously rub the entire grape bunch between my hands, crushing up the brittle stems. I did this over the mesh solar dehydrator screens, which allowed most of the stems to fall through the cracks, while catching most of the raisins. Some of the smaller raisins did fall through. But within a short while, I had the screen covered with raisins (many with short stems attached), and only some stem litter.
Next I shook the screen a bit to encourage more stem bits (and incidentally more small raisins) to fall through the screening. Finally, I spread a couple of dish towels on the table at the far end of the screen, tilted the screen so the far end rested on the towels, and shook/pushed with my hand all the raisins down onto the towels. Funneling the raisins from the towels into jars took very little time from there. I still had to pick through the stem litter on the table to pull out the small but usable raisins, but at least it took way less time than my original one-by-one method!
I assume people have perfected easier ways of processing raisins, starting with not over-drying their grapes. I wonder whether commercial growers selected certain raisin varieties such as Thompson's and Flame in part for ease of processing...I don't know much yet about what makes a good raisin grape. Plenty to learn...but at least I know one relatively quick way to deal with crisped raisins!