grrrr while I was answering
Controlled bubbles are indicative of the use of a mould, I think there is a picture of one lurking somewhere around these forums. Basically a mould with lots of points.
The item (Blob of glass on the end of the pole) is dipped into the mould and then (cased) covered in more glass, wherever the points pushed the first layer in, a small amount of air is trapped creating a bubble.
The bubbles can be distorted by manipulations.
In fact they can be added by hand with a pinwheel or just a pricker.
Random shaped bubbles are created by sprinkling vapourising granules onto the item before casing.