The glass used in electric bulbs is very thin, yet is able to withstand breaking when you hold it. The reason, its shape is the answer and uses the eggshell principle.

Natures is mostly to thank for this principle, for evolution has created an egg that is thin enough for the young to break out, yet strong enough to withstand the mother weight when incubating the eggs. The key is in the structural shape of the egg as it is able to withstand all-round pressure.

It works by the pressure being transmitted all over the shape therefore weakening the force applied to it. It is transmitted by the shape being round and curved all over the shapes area.  That is how they are strong but how are they made?

The making of bulbs is very intricate and starts by a ribbon of molten glass blown into shape in moulds. Whilst the glass is hot the stem is clamped onto the base of the bulb and the oxygen in the bulb is removed to stop the filament oxidising. Instead the bulb is filled with a argon/nitrogen mixture, and sealed with a metal cap. A bulb building machine can make 30 bulbs in a few minutes and each able to light up a room for over 1000 hours.

In a nutshell.

1. Molten glass is blown into shape of moulds.
2. Whilst it is hot, the stem is fused with the base of the bulb, and oxygen is replace by a argon/nitrogen mixture.
3. The stem and base are soldered together.