Concur w mso. I, in 30, years have only ‘bubbled‘ one pipe, and that one, while defective, I indeed smoked too hot. If it is hot to touch, it’s smoked too hot. Slow and cool is a challenge. Best of luck.
agree with MSO - I've never seen a pipe finish bubble. I have several that appear to have some sort of clear coat (Rattray's, and Brebbia) that are super glossy but have never given any issues.