I've been pushing the envelope slowly with regards to the dimensions of my glass feathers; I'm really not sure how large they could get. I've just started sculpting a Great Horned Owl feather that measures 16" x 4.5". Those birds are so huge, this is only about 30% larger than life-size. But this post is about the smaller end of the scale, as I also tried making some jewelry-sized feathers. The longest feather in this group is 5.5 inches long.
The results have been very satisfying, and I let these be completely experimental regarding color combinations, instead of trying to emulate the feathers of a particular bird. Some of these beauties have a metallic shimmer from a bit of added mica. I made a trip to Santa Fe Jewelry Supply for findings, which is a mind-blowing experience. Who knew there were so many little geegaws for jewelry-making?