Question about pontil bottles?

[gdog68]

This is a pontil case gin for the mid 1800s I believe, I looked at the picture online and I noticed the lack of air bubbles and was wondering if this is because of the craftsmanship of the glass makers(does experienced glass blowers produce less bubbled glass or is it other factors) ? Does extremely bubbled glass determine age range?

 

[CanadianBottles]

I'm not sure what exactly causes bubbles in glass but it's not very reliable for dating bottles beyond bubbles not showing up too much within the past century. Plenty of pontil bottles have very few bubbles and I've seen some very bubbly glass from around 1900-ish (mostly from outside North America). I'm also pretty sure it's not the glassblower who causes the bubbles, I would assume it's something to do with the chemical composition or heating of the glass.