I’ve had some fun with copper foil. It provides blue bubbles if using only a single layer. That was a happy accident.
Someone told me that a mixture of copper oxide and CMC can also produce blue bubbles. I have yet to try this– real life keeps getting in the way of playing mad scientist at the kiln. I got a recipe that I traced back to Tom White in Texas: 100 parts P-25 ceramic frit to 10 parts of copper oxide black in a 2% solution of CMC gum. Again, I haven’t tried it.
I did small “crumbs” of baking soda and borax dry that turned out okay as bubbles. I’ve experimented with putting the textured side of glass together. With a thin reeded glass, the bubbles are consistent in size and pattern. I keep trying for a “spray” of bubbles, and the best was the copper foil since the color added a nice bonus.
Hopefully someone has more experience with creating bubbles or has used the bubble powder that Delphi and others sell.