Glass blowing is by definition a hot process! The transformation of raw materials into glass takes place at around 1,320 °C / 2,400 °F, and the glass emits enough heat to appear almost white hot.
The glass is then left to "fine out" (allowing the bubbles to rise out of the mass), and then the working temperature is reduced in the furnace to around 1,090 °C (2,000 °F).
At this stage, the glass appears to be a bright orange colour as seen here.
Glassblowing involves three furnaces. The first, contains a crucible of molten glass, and is simply referred to as "the furnace". The second is called the "glory hole", and is used to reheat a piece in between steps of working with it. The final furnace is called the "lehr" or "annealer", and is used to slowly cool the glass, over a period of a few hours to a few days, depending on the size of the pieces. This keeps the glass from cracking or shattering due to thermal stress.
So much work goes into each piece. All bubbles & forms do vary a little, as is only fitting for somehing that is crafted in this way.