How can bubbles form in a hand blown solid glass round earth shape object?

Question

I bought this object (the shape of the Earth) years ago. Then when I moved to FL. and had it on my mantle in my living room there appeared many shape bubbles coming from the botton of the object. Even the artist cannot tell me what is going on. Can you?

Thank You

MF

Answer 1

Becuse heat causes steam to rise and bubbles are a result of the steams natural energy