The Carbon filaments days were now numbered, for twenty years the manufacturers had looked for cheaper and more durable materials for the filaments. The final choice, tungsten, was first sold in Europe in 1906. But it was not until after 1910 that technological advances made it the best option. Throughout this period filaments in a wide range of metals were developed. From 1906 the power stations saw a steady decrease in demand as more people switched to efficient metal filaments, but they recognised this as the lull before the storm, it gave electricity a real price advantage over gas and would increase installations. In 1909 the smallest metal lamp for 230volt supplies gave 50 cp. and cost 4s. 9d. , the lamp only cost 7d to make, at the same time the 16 cp. carbon lamp was only 9d and it was harder for the consumer to recognise the advantage. The power companies did not advertise this fact, the manufacturers being willing to let market forces dictate the rate of changeover. At this time the average wage was 30s a week. Life span of the new bulbs averaged at 1,100 hours with a maximum of 6,000 hours being recorded.

By 1910 the power industry began to accept that the improvements to the consumer were a permanent loss to the industry so began a more concerted effort to sell or hire other electrical appliances to the consumers. The electric fire had just been improved to make it a practical option and in almost every area of the home an electrical appliance was on offer. Also instead of increasing the price of electricity they began to reduce it and offered cheaper installations in private houses. Some companies tried to prevent their customers from switching to metal bulbs but found that they had no legal rights to do so.

Baron Carl Auer von Welsbach born in 1858 in Austria. He was primarily a chemist and invented the incandescent mantle for the gas light. In his experiments with rare metals he found a method of making an osmium wire from which he produced an efficient filament bulb in 1898. It was very fragile and had to be burnt base up to prevent the filament from sagging and breaking. He patented it and set up the Auer Company to manufacture and market the bulb in 1899. The Auer Company became a part of the Osram Company in 1919. He died in 1929.

Austrians Franz Hanaman and Alexander Just made a tungsten lamp in 1903. This was made by depositing tungsten onto a carbon filament. The process was not suited to production though.

Hans Kuzel adapted Auer’s osmium squirting process to tungsten. Because the wire was very fragile the filaments were made up of several short strands in a cage like arrangement. Auer’s company produced these lamps in 1907. The Netherlands firm Philips also used this process from 1908.

By 1903 the Nernst lamp had become quite important, it was used in Buckingham Palace and for the clock faces of ‘Big Ben’ on the Houses of Parliament as well as for street lighting and some domestic users. It gave a fifty percent saving in current and light equivalent to eight of the 16cp Carbon lamps. The bulbs cost 3s. 6d. each against 1s. each for the carbon lamps. The main disadvantage was that the Nernst Lamp took about half a minute to light up as it had to get hot first. Earlier lamps could be started with a match! It suffered from poor manufacturing standards which resulted in a fairly inconsistent life span. They were used in Maidstone in Kent, England, for street lighting where the Authority recorded some lasting for two or three thousand hours but others would fail after only one hundred hours, overall they found an average life span of 676 hours. Another problem was that the light output fell off considerably during their life and also varied in damp weather.

Dr Werner Bolton and Otto Freurlin, head of Siemens & Halske’s incandescent lamp works developed a tantalum filament after Werner had found a method of making wire from it in 1903. Siemens, realising the importance, manufactured and stockpiled the bulb in large quantities while setting up world-wide patents. In 1905 the tantalum bulb was launched world-wide, it had straight sides sloping out from the base and the long filament wove its way around the bulb over 23 small hooks. In 1907 they developed an alloy of WOlfram (tungsten) and TANtalum which was marketed as the WOTAN bulb. It was quite successful and was in use from 1905 to 1914 the WOTAN name is still used today. Siemens Brothers & Company Limited opened a factory to produce these bulbs in Dalston, London, in 1908.

AEG designer Peter Behrens developed an arc lamp for domestic use but no development work was undertaken for incandescent lighting. Their lamp making department became a part of OSRAM in 1919. Peter Behrens also lays claim to having being the first Industrial Designer.

The name OSRAM was introduced by the German company Die Deutsche Gasglülicht (Gas glow lamp) Gesellschaft for its Osmium lamp.

Edison & Swan United Electric Light Company Ltd, as they were known in 1906 sold their metal filament bulbs as the ‘Royal EdiSwan’. The standard bulb, with either bayonet or screw thread had three or four loops which required an additional central support. The in lead wires and this support were fitted into a single flattened glass support.

The American General Electric Company, now known as General Electric and unrelated to the British company G.E.C., developed the GEM lamp with a ‘metallised’ carbon filament that gave a 25% improvement in efficiency. Willis Whitney, in 1905, found a heat treatment for the carbon filament that changed its temperature to resistance from a negative one to a positive one. Metal filaments have this characteristic and it is because of this that they were described as metallised. They introduced a tungsten lamp in 1909 and named it after the Persian God of Light ‘MAZDA’.

American William Coolidge developed a process for making ductile tungsten in 1910. Tungsten that could be drawn in long fine wires. This was introduced in the OSRAM lamp world-wide in 1911.

Tungsten filaments were introduced to England by the British company G.E.C. in 1906 as the OSRAM lamp. In 1907 they also marketed Siemens WOTAN lamp. Royal EdiSwan were first with a non-ductile tungsten bulb in 1908 called the METFIL lamp. G.E.C. marketed a non-ductile tungsten OSRAM lamp in 1910. By this time the three most commonly used filaments were carbon, tungsten and tantalum. The power requirements for these three varied, Carbon used 3.5 Watts per cp., Tantalum 1.7 Watts and Tungsten 1.2 Watts. An advert for OSRAM car bulbs in 1914 shows a cap-less wire loop bulb. The Carbon lamp survived because it was still the cheapest to buy. Tantalum was only used on DC. circuits and Tungsten was suitable for either AC or DC. Bulbs from this period are often found marked with both AC and DC. ratings.

In 1913 a new alloy ‘DUMET’ was found to replace platinum as the lead in wire. It is a composite wire with a layer of Borate over a layer of Copper over a Nickel Iron core. It adhered well to the glass walls of the lamp and also expanded and contracted, with heating, at the same rate as glass thereby reducing leaks which destroyed the vacuum in bulbs.

American Irving Langmuir discovered that minute portions of water vapour in an evacuated lamp reduced the filaments life by evaporation of the element. Because of the heat loss through the gas he coiled the tungsten filament to compensate. The American G.E.C. made a lamp filled with Nitrogen in 1913 which reduced the rate of evaporation and allowed the lamp to run at a higher temperature therefore giving off more light. By 1918 lamps were being filled with Argon thanks to Cooper-Hewitt finding a method of separating the inert gases from air.

Philips and others produced gas filled coiled filament lamps from 1914. Although marked ‘½ WATT’ they only achieved about one watt per candlepower output. Philips ‘½ WATT’ lamp was quite large and intended to replace the arc lamp. Their ARGA lamp was also a coiled filament gas filled lamp but of standard size.

The first Swedish company to manufacture bulbs was the Scandinavian Incandescent Lamp Company of Nyköping in 1904. By 1909 half a million lamps were in use in Stockholm.

A non-sagging tungsten filament was developed in 1917.

Most bulbs had the ‘pip’ seal on the crown. Some examples of decorative bulbs appear to have had the pip flattened and polished smooth. In 1919 an easier method of making bulbs without pips on the crown was developed. Air was extracted from the base and the bulb was sealed there. Over the next few years all the largest manufacturers changed to this method but the pip continued well into the twenties for low volume types. Some modern bulbs of a specialised nature still appear with a visible pip.

In 1910  8 cp. or 16 cp. high voltage Carbon filament lamps sold for between 9s. and 10s. per dozen. Osram tungsten bulbs of 10 cp. to 32 cp. for 25 to 50 volts sold for between 2s.3d and 3s. each! Tantalum bulbs of 5 cp. to 16 cp. for the same voltage sold for between 1s.6d and 2s. each. Running costs for a small flat with eleven lamps, averaged over three years use, was £2.2s.0d for the electricity plus 2s. per quarter for meter rental using carbon filament lamps. In another case with 41 lamps of mixed types, 8 cp. carbon to 50 cp. metal filament the average cost was £6.17s.4d per year. In the first case the unit cost averaged out at 4d and in the second 5d per unit. For comparison a skilled wireman (electrician) would earn up to £2 per 53 hour week or £100 per year.

In 1902 the electrical trade set up ‘The National Electrical Contractors Association’ to raise opposition in Parliament to the granting of powers to Municipalities for the retailing of electrical apparatus and fittings in the premises of customers or would be customers. From 1903 - 1905 they prevented the London County Council being given powers but were defeated in 1906. With the 1909 Electrical Lighting Acts Amendment they succeeded in including a clause that obliged the municipalities to use a registered contractor for installation work.

The Provincial Incandescent Fittings Company set up in 1900, marketing gas lighting accessories began to make and sell small battery equipment and miniature bulbs under the trade name of PIFCO to which they renamed the company in 1949. Normal domestic light bulbs were also made by PIFCO.

In 1919 the German light bulb manufacturers, AEG, Siemens and Auer, pooled their resources and formed the OSRAM company to keep their position in the world market.

Next Chapter - The Incandescent Lamp, 1920 onwards