Indoor lighting
What do you do when it gets too dark to see at home? You flick a switch and light appears almost instantly. In the past it was not as easy to light your home.

Imagine that you lived about fifty thousand years ago. Your home then may have been a cave or a tent made from animal skins. In either case, when the Sun went down, you would have been left in the dark. However, at that time, people could make some light of their own. A hole was made in a wooden block and a stick was placed in the hole. The stick was twisted round in the hole very quickly and very dry pieces of grass were placed close by. The rubbing of the stick in the wood block made a great deal of heat. Eventually the heat became so great that it made the grass burn. This was then used to light a fire.

The fire provided light to help people see and heat for cooking food, such as meat. As the meat cooked over the fire, fat dripped from it and fell into the embers. When the fat hit the embers, it became so hot that it burst into flames and gave extra light. This gave people ideas about using fat and oil for lighting.

As long as forty two thousand years ago people had discovered how to make oil lamps. Each lamp was made out of a piece of stone. Part of the stone was hollowed out to make a cavity. Oil was placed in the cavity and a piece of moss drenched in animal fat was placed with one end in the oil to make a wick. When the other end of the wick was lighted, the fat burnt away and was replaced by oil that crept up the wick. The oil lamps could be taken into caves to help people explore. The lamps were also used to provide light so that people could decorate cave walls with paintings.

Oil lamps were used for over forty thousand years but other forms of lighting were also developed. If you look in some fields near water, you may see plants with clumps of dark green spikes half a metre or more in height. These plants are called rushes and they grow in damp soil. Although the spikes look like leaves they are actually stems, and if you break one open, you can see a spongy material inside. These stems used to be soaked in animal fat, then the tip was lit and it burned like a candle for about half an hour.

Candles were made by dipping threads in animal fat and letting the fat set hard around them. The tip of the thread was allowed to stand up above the fat and form the wick. When the wick was lit, animal fat in the thread burnt away. The heat from the burning fat melted fat at the top of the candle and this freed the wick to be burnt. Candles were a great improvement on rushlights because they burnt for up to eight times longer.

Candles made from animal fat not only provided light. They produced a strong smell as they burnt. Fortunately it was found that beeswax could be used to make candles. A beeswax candle gave a stronger light and a pleasanter smell. As the supply of beeswax was much smaller than the supply of animal fat, beeswax candles were more expensive and only wealthy people could use them to light their homes.

In 1784 Aime Argand, who lived in Switzerland, made a new kind of oil lamp. It had a glass chimney around the wick and the wick was much larger than those on previous lamps. The chimney allowed a current of air to be drawn over the wick which increased the speed at which the oil burnt. This in turn made a brighter light. Many of these lamps were fitted with a shade of white glass, which helped to spread out the light. These lamps used oil from fish, whales and olives. Some also used beeswax and animal fat. However in the middle of the nineteenth century a new material was used to provide light. This was a liquid called paraffin. It was made from oil, which formed under the ground.

While paraffin lamps were replacing oil lamps another form of lighting was being used more frequently in the home. This was gas lighting. The gas was made by heating coal. As the coal was heated, gas escaped from it. The gas was collected in a gasholder then piped to homes.

As gas lighting became more widely used the last source of light was developed ? the electric lamp. In time electricity replaced all other forms of lighting as the major source of light in the home. To get an idea of how important electric light is in your home count the number of lamps.

How did early people heat the wood enough to make grass burn?
The top end of a stick had a piece of cord wrapped round it and the cord was attached to a bow. Moving the bow to and fro made the cord turn the stick in the block of wood. By moving the bow quickly the stick would turn even faster and the heat built up with the two surfaces rubbing together. If you rub your hands together you will feel them get warm. The force which acts when one surface rubs on another is called friction.

Did everyone use candles, rushlights and oil lamps?
Rushlights were the cheapest lights to make. You simply gathered rushes from wet fields and soaked them in fat, which you collected from the meat you cooked. Rushlights were used by poor people. Wealthier people used candles and oil lamps.

How did oil form under the ground?
It formed from the bodies of tiny plants and animals that lived in the sea over two hundred million years ago. When most plant and animals die, their bodies rot away. However when these tiny plants and animals died they sank to the bottom of the sea but did not rot away completely. Their bodies formed a dark coloured liquid called petroleum. This liquid is also known as oil. It is a mixture of substances. Some of the substances are used to make petrol and plastics.

Are candles made from animal fat today?
No, they are made from some of the substances in oil. These substances form a material we call candle wax.

What happens to oil and candles when they are burnt up?
The oil and wax is changed into water and a gas called carbon dioxide. You do not see the water because it changes into a gas called water vapour in the air.

Is air needed to produce light?
It is needed by things, such as wood, fat, oil candlewax and gas, which burn to produce light. Air is a mixture of gases. One of the gases is called oxygen. This is the gas that things need if they are to burn.

Did gaslights simply have flames like you see on a gas hob?
Some early gaslights did but then a special device called a mantle was developed. This was a fine piece of netting which fitted over the end of the pipe which released the gas. When the gas was switched on and a flame was placed near the mantle, the gas began to burn and the heat made substances in the mantle shine brightly. It was the shining of the substances in the mantle that produced the light.

Is gas lighting used today?
It is not used in homes but may be used to light caravans, boats and tents. The gas that is used in these lights is stored in a cylinder. This gas, like oil, comes from the ground. It is called natural gas and is made by the decayed bodies of tiny plants and animals that lived in the sea two hundred million years ago.

Did people use natural gas in the nineteenth century?
No. It had not been discovered then. They used gas made from coal. Coal is a black substance formed from trees that lived in swamps three hundred and fifty five million years ago. When the trees died they fell into the swamps and did not rot away completely but formed the black fossils called coal. In the nineteenth century coal was heated in a furnace and gas was released from it. This gas, called coal gas, was used to provide lighting and heating in homes. Today coal gas is no longer used. It has been replaced by natural gas.

How does an electric light bulb work?
In the centre of the light bulb is a thin coil of wire. When the bulb is switched on, a current of electricity passes through the coil and makes it become so hot that it glows and gives out light.

Does a strip light work in the same way?
Some strip lights, such as those used under cupboards or over hobs in kitchens, have a coil of wire and work in the same way as a light bulb. The strip light in a ceiling in a kitchen or in a classroom works in a different way. When a current of electricity passes through it the white coating on the inside of the glass tube shines. This material is called a fluorescent material and the strip lamps are called fluorescent lamps.