Stem finishing question

[sstodvictory]

From examining pipes in my collection that have transparent stems, I have noticed differences in the finishing of the lumen of the stem bore. Some lumens are completely smooth and transparent, polished to the same finish as the outer surface of the stem. Others are smooth but not polished to complete transparency.

My question is, for those finely-polished stem lumens, how is it achieved? Is heat involved? Is it done with a pipe cleaner with fine grit applied, or what?

Steve

 

[Sasquatch]

Smooth files in the slot, and drill bits in the bulk of the airway both leave half-decent surfaces, and to take them from half decent to polished you use tripoli compound on a pipe cleaner.

I'm not sure if some clear stems are cast with an airway in place or not.