I finished another batch of tests using the powders on fiber. Almost all of them came out so well.
As I was cleaning the glass pieces getting ready for the final fuse firing, I dropped one of the pieces and it broke into three parts. How clumsy! I didn't expect it to work, but I placed the pieces on black glass and covered the top with a layer of crystal clear powder. It's the top piece shown below. It fused beautifully, without a trace of the breaks!