Prune After the Lye Bath
This picture shows the Giant Prune as it appears after being dipped in lye to produce the cracking of the skin that will factlitate drying. This is the final test that a prune must pass. If its skin does not crack properly, or if its sugar content is insufficient, the prune will not dry rapidly enough to escape fermentation. Many prunes that are otherwise of fine quality cannot meet this test.
This image is from: Luther Burbank: his methods and discoveries and their practical application. Volume 2 Chapter 8