Fine bone china mug ‘Cherry Blossom’ 0.35 l.
Handblown
All double–walled glasses have a small hole at the bottom, which is firmly closed by a synthetic resin membrane. This membrane serves to equalise the pressure of the double–walled glass layers and ensures that the glass does not break despite extreme temperature fluctuations.
Okan –
The space in between the two layers of ceramic is filled with air. When air heats up, it expands. Every time you pour a hot drink like coffee or tea into your mug, it heats the air in between the layers, causing it to expand. The hole offers a path for the expanded air to escape