There was now the tungsten filament, the standard bayonet, ES screw caps and the familiar pear shaped bulb. All the elements of our modern light bulb. Still to come were the internal frosting, the coiled coil filament and major improvements in efficiency. However, we have now passed the age of the gentleman inventor, the First World War caused major social upheavals in throughout the world. Trade unions had gained greatly in their strength and the working classes were demanding better conditions. The industrialists, tooled for war, needed to re-direct their machinery to peace time uses. The light bulb and cheap electricity were ripe for development into this new technological age. The sophistication of manufacture was going to see rapid improvement. Immediately after the war most light bulbs were still hand-blown and the increase in demand was starting to put a great strain on the skilled glass-blowers. The speed of change needed required huge expenditure and the lone worker could no longer compete, although individuals continued to contribute greatly. Most of the developments in lighting were now being made by big businesses and while individual names are often linked to important developments they were mostly employed by the companies. For the study of light bulbs this period is fascinating as the old and new technologies often overlapped, carbon filament bulbs were still being produced for their heating properties. Frustratingly, frosting makes it impossible to see inside and examine the construction but most types were and still are made in clear versions. Of particular interest in this period was the sheer variety of special purpose lighting that was developed as the uses for electric lighting became more diverse. Perhaps the biggest leap is the development of electro-luminescent materials, although their use was largely restricted to industrial equipment and photocopiers. The micro-chip is also developing with light, microscopic light sources sending signals via fibre-optic paths instead of electricity.

W. Fenton and J. Ridington of the USA patented a dipping car headlamp bulb in 1924. In 1937 the sealed beam headlamp was introduced in the USA.

Internal frosting of bulbs was introduced in 1925. Before this bulbs had been either acid etched or sandblasted on the outside if a frosted effect was wanted.

In the United Kingdom the Electricity Supply Act of 1926 established a Central Electricity Board. This body was given the power to control the distribution of electricity and allowed a standard voltage and frequency of AC Electricity. By establishing the National Grid it was able to provide a unified distribution for the whole country. A standard frequency, the number of times that the polarity reverses, of fifty cycles per second was chosen for the UK. The USA chose a frequency of sixty cycles for its power supplies at 115 volts.

Construction of the British National Grid commenced in 1927 and was virtually completed by 1935 the first section opened in 1929.

The coiled-coil filament was developed in the USA in 1934. The extremely fine tungsten filament being coiled and then the coil coiled again, this trapped the gas in the coils creating a brighter and more energy efficient light.

By 1938 65% of British homes were connected to the mains electricity supply. This figure rose to 96% by 1961.

Very high power incandescent bulbs were developed for lighthouse use from 1922. Xenon filled lamps were developed in 1947. Used in lighthouses they increased the effective range to 20 miles.

In the 1950’s Siemens & Osram developed Metal-Halide lamps which gave a five times increase in light output for no power increase over tungsten. These lamps came into popular use after their use at the Olympic Games in Munich, Germany. In 1973 they introduced the LUMILUX fluorescent lamp giving more light for 10% less power! When in 1978 Siemens took full control over Osram they were the world’s fourth largest lamp manufacturer. The Osram CIRCOLUX bulb of 1980 is a fluorescent tube in a bulb giving the equivalent of 75 Watts for 25 Watts of power.

Lumalampen AB was set up in Sweden in 1929 and opened a factory in Stockholm to manufacture LUMA bulbs. Since 1936 they have produced their own tungsten from Swedish ore. They began to manufacture fluorescent lights in 1943. They moved to Karlskrona in 1970 and are now the only lamp manufacturer in Sweden.

Useful electric power was first produced by a nuclear reactor in America in 1950 but the first nuclear power station for commercial use was opened at Calder Hall, England, in 1956.

In 1951 the British company G.E.C.’s catalogue contained a wide variety of lamps many of which were for very specialised uses under the Osram marque. For mine use there were Krypton filled bulbs giving a 20% increase in light output for no power increase. For the film studio there was a ‘2 kW Compact Source Colour Corrected Lamp’ which was a high pressure mercury vapour discharge lamp and was advertised as a replacement for carbon arc lamps. Colour correction was achieved by adding Cadmium vapour, they had an external pip and they cost £40 each. They also still sold at £2 each the ‘Robertson’ Carbon Filament Radiator bulb, used as the heating element in a type of electric heater, ‘The Dowsing Radiator’, developed in 1912. Standard Osram bulbs were available from 15 to 1,500 Watts for voltages from 25v to 260v gasfilled and vacuum bulbs for 15 and 25 Watts for the same range of voltages.

A high pressure sodium lamp giving a golden white light was developed in 1957.

The laser (Light Amplification by Stimulated Emission of Radiation) beam was invented in 1960 by American T. H. Maiman (b. 1927). As yet of little use in the home, except for CD players, they were first used by Siemens for stage lighting effects at the Munich Opera festival in 1970. It is used for communications by glass fibre cables, building alignment, machining in manufacture and very fast computer printers. The laser beam is an intensely concentrated beam of coherent light.

In 1961 the Quartz-iodine bulb was developed. Thorn Lighting developed compact source iodide (CSI) lamps in 1969. In 1981 Thorn introduced the 2D lamp producing 100 Watt equivalent light output for 20 Watts of power, it is a fluorescent tube folded up into a bulb which contains all the driving circuitry. It has a design life of 5,000 hrs and is priced to give a small economy over tungsten bulbs. Very recently versions have appeared that contain all the circuitry in an almost standard sized bulb with standard fittings.

The newer developments have little to do with the incandescent filament. Perhaps in the future it will vanish completely. Maybe someone will make a radical new development. Whichever way the lightbulb develops it will continue to be taken for granted in use. The early lightbulbs are now sought after by collectors and will be around for longer than most modern bulbs. Bulbs from 1890 onwards are fairly easy to obtain and many of them are very attractive objects in themselves.

Next Chapter - Other Types of Light