Here is how I make trapped bubbles. You will need:
two pieces of translucent glass cut to the same size in the shape of your finished jewelry, some stringer, diluted glue and a small paintbrush.
Break your stringer pieces so they are just a little bit smaller than your base and top. Clean all the glass .
Start with the inside surface of the bottom piece. Apply the diluted glue to it where you are going to put the stringer. Wait a couple minutes for the glue to get tacky. Place pieces of stringer on the bottom glass. Make sure there is space between them I end up using tweezers to get them exactly right Set this aside to dry.
Follow the same process for the inside surface of the top piece. Glue the stringer in the opposite direction so that it will form a little grid when it is placed together with the bottom.
Once the two parts are dry, you can gently lay the top piece on the bottom one. I usually do this on the kiln shelf so it won’t have to be moved again.
Fire using a normal jewelry firing schedule.
Since the stringer is smaller than the base and top, the edges will close nicely. The stringer grid traps bubbles in each little square.