How are light bulbs made?

Find out with Sir Sidney McSprocket!

Sir Sidney McSprocket’s been in action capturing facts – all about manufacturing!

Today he’s finding out all about light bulbs!

Sidney’s all for having a light bulb moment – it’s part of what being an inventor’s all about!

But have you ever wondered how incandescent light bulbs – they’re the older style bulbs – are made?

First you need to know that there are three main sections to a light bulb – the glass shell, the filament that glows and the base that holds the bulb securely.

To make the shell, the raw materials for glass – sand, soda ash and limestone – are mixed and heated. The molten glass is carried along a conveyor belt and air nozzles blow the glass through holes in the belt into moulds creating the shape of the shell.

Such a machine can produce more than 50,000 bulbs each hour! Once cooled, the inside of the glass is coated with a protective chemical to reduce the glare caused by glowing.

The filament is made out of a fine wire that’s wound around a metal bar called a mandrel to mould it into its coiled shape. It’s then heated to soften the wire and makes the structure more uniform, before the mandrel is dissolved in acid.

The base of the bulb is assembled from a tiny little circuit board and a plastic casing with indentations in the shape of a screw so that it can easily fit into the light base.

It’s also labelled with information about the bulb, such as how bright it is.

The different parts of the bulb – the glass, the filament and the base – are then assembled by a machine.

The air inside the bulb is taken out and replaced with a gaseous mixture of argon and nitrogen which help ensure a longer-life for the filament.

The bulb will be tested to make sure they’re up to the job. They’re tested upside down too – after all, lots of lights are on the ceiling!


Sidney McSprocket is Fun Kids’ resident inventor!

When he’s not in Edinburgh, tinkering with wacky contraptions in his workshop, he’s finding out all about manufacturing!

In the latest series, Sidney is finding out about a whole load of everyday objects from tin cans and toothbrushes to plastic bottles and Pyrex…

Sir Sidney McSprocket's Amazing Inventions

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Sidney McSprocket’s How’s it Made, with support from the Royal Commission for the Exhibition 1851.

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