I took a class to learn how to hand blow ornaments, where a blow torch was used to heat the glass. This was much more difficult then I expected. Glass is finicky. My first ornament broke because it suffered shock from too much thermal change. The amount size and amount of fritz, the shattered glass bit added for color, changes the amount of breath you need get it to expand. You need to blow correctly, in small puffs.
Here are the results. The broken was my first attempt. I saved it because I love the color. The two that a ball shaped had the fine powdered fritz. Using the heavier fritz, I ended up with large Christmas light bulbs.
I have some ideas on how to improve my technique. I might try this class again next year.