purposly done air bubbles in marbs like that look boss!..but air bubbles in like a heady glass pipe or some shit is most likely from the artist boiling the glass, not a good thing lolol.
Not quite true, but it could be true...... If you take a pastel color (like orange or red crayon) and just introduce it into the flame, that's bad. You want to kiln the rods for a minute or two, then apply the rod to whatever your doing, and then re-kiln it for a few minutes again. Then you can work the shit out of it. Additionally, some people cover their pastels with clear (encasing), to prevent any boiling. This practice, oddly enough, can cause you to trap air bubbles while layering the clear down.
Air in a really heady piece doesnt mean that its made from a poor glass blower either. It could be air trapped in pre-made tubing that the artist purchased, it could be a stone or imperfection in the glass, etc..... Of course, an artist making that really heady piece wouldnt sell it after seeing the bubbles develop while making it, either.
The worse way to continually get bubbles in your glass is to use the first 4mm of the glass rods on either end. Those are the pieces that are going to bubble the worse. Heat that up, pull it off, then apply the rods and you'll find great success..........
It takes skill and care to get it right. 
