I have not yet, personally turned this material. I look forward to doing so.
What I can tell you is this is probably poured in sheets. Often, near the end of the sheet, the material does not quite hit the frame and there are bubbles, sometimes many and large, in this area. One would expect that the person cutting the sheets would discard these. I believe they USUALLY do. But, I have also seen blanks delivered to us (Acrylic acetate, not this new stuff) that DO have bubbles.
When you finish a pen and are not sure if you have tool marks or air voids (bubbles), look at the shape. Tool marks are irregular and usually not very deep. Air voids have clean edges and are usually round. They are also usually similar in depth and diameter (like a round bubble).
Just a little info on all resins, may or may not apply to your present situation.
The advice to clean the dust out thoroughly is ALWAYS correct. Not always easy. Good luck and good turning!!