WarmGlass.com

I know where bubbles come from, really. The issue is, I swear to goodness when I took these pieces out of the kiln they were bubble-free. And now, several hours later when I took them off the shelf to do the next phase of work, they have bubbles. Is it at all possible that air bubbles can somehow form after the piece is cool enough to touch? Or am I just that unobservant that I somehow failed to notice?

(These are not large pieces - 6mm thick, smaller than 20 cm square.)

Not possible for bubbles to form when cold.

You just didn't notice the bubbles when you took the piece out. Sometimes you have to hold the piece at angle to see small bubbles - it that's the issue.

you took them off the shelf. That white shelf hides a ton of stuff!!

Thaaaaat's what I figured. I look more closely now, you betcha.