All Ojinika Glass products are handblown and flameworked using top quality borosolicate glass.
Borosilicate (hard) glass is a type of tempered glass known for it durability and ability to resist thermal shock. The common name for it is Pyrex.
It is mainly used in kitchen cookware and scientific laboratory glassware. It is considered "unbreakable" compared to the common soft/soda-lime glass.
To maximise strength, each piece is annealed in a kiln after being shaped in the torch flame.
You can learn more about the science of borosilicate glass HERE: