Painted vellum bindings: German Pietism

A few days after writing on painted vellum and with the subject still kind of murmuring in my head, I came across this beautiful, almost modern art, vellum binding on a typically Pietist German book, the Güldene Rose by Christoph Schütz.
Not unlike Jansenist bookbindings, Pietism seems to have developed an aesthetical standard of its own.

Mostly clad in solemn black on the outside (remniscent of the Dutch sharkskin tradition in Bibles), they often have fine brocade endpapers, - and even more baroque illustrations. This booklet, however, seems to imitate tortoise bindings in an abstract way. The technique is probably a simple bleach-out (unfortunately also often heavily deteriorating the leather, as are the diverse way of bleaching, staining and marbling with vitriol that were popular in the 18th century).