Posted 10 years ago
Spiraloptisch is a relatively rare decor - I've only seen a few, and they always seem to be on unpublished forms. This one is Cristal with gradient dark green, circa 1905. Other examples can be seen on Eddy Scheepers's excellent Loetz.com website, including one in Candia silberiris in this shape but with a ruffled rim.
I don't know what the real story is, but it seems to me that the inspiration for this elegantly simple decor may very well have been a Japanese Zen garden (see last photo) - Art nouveau has its roots in Japanese design influences, so it seems like a logical theory.