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A Short History of Electric Light
by Frank Andrews
Sir Joseph Wilson Swan Swan was born on the 31st October, 1828, in Sunderland, England. His qualification as the inventor of the light bulb has always been a matter of contention. Principally because the long legal debate between Swan & Edison was settled out of court, the two parties burying the hatchet and combining their resources into one company that marketed the incandescent light bulb. As a team they were formidable, their combined patents preventing any serious competition until 1893. His lectures in 1879, January 17th in Swan Lectures. Sunderland, February 3rd in Newcastle and March 12th in Gateshead, are a matter of record. During the Edison v. Swan court actions, evidence was given proving that the incandescent filament was demonstrated at the Newcastle lecture before Edison’s demonstration. This lamp was almost certainly made using a very thin rod of carbon as the conductor in a vacuum. During that year he invited Colonel R. E. B. Crompton to his laboratory who reported seeing twenty bulbs burning.
He found a method of fixing the element to the platinum lead-in wires and discovered that by heating the filament during evacuation the vacuum was enhanced and blackening of the glass greatly reduced. He applied for a patent for the heating of the element during evacuation on the 2nd January 1880. Normally a small amount of air trapped was absorbed in the filament (occluded) and its release when the bulb was first used decreased its useful life. It was this patent which gave Swan the leverage in combating the Edison patents two years later. Despite the suggestions of his friends Swan was reluctant to apply for more basic patents as he felt he had only developed the work and ideas of others. By this time his filament was made from carbonised paper and during 1880 he developed a filament from parchmentised cotton. At a meeting of the Newcastle Literary and Philosophical Society on the 20th October 1880 he gave the first public demonstration of his lamp. Another display powered by a Crompton dynamo in Glasgow resulted in the first commercial sale to the Glasgow General Post Office.
Swan began his career as a chemist in partnership with John Mawson where he developed a reputation as a photographic consultant. In 1864 he was granted a patent for a ‘Black Carbon’ non-fading photographic print. He later invented the silver-bromide print which is still in use today for black and white photography. He began to study the incandescent filament in the 1840’s when he saw it as being of potential use for photography and as a safe illuminant in coal mines. During the 1850’s, having discarded the idea of using platinum filaments, he began to experiment with carbonised paper and card.
He had a container filled with carbon dust and strips of paper heated to white heat in a pottery kiln. He used the pottery of J. J. Wallace & Co. (1838-1857) at Forth Bank Pottery, Newcastle upon Tyne. When cooled the pieces of card had been carbonised and become elastic although it was slightly brittle. He fixed a one inch arch of the “ wide paper between carbon blocks connected to wires over which he mounted and sealed a glass shade, then exhausted the air using a pump built by the Reverend Robert Green of Longhorsley. When connected to 40 or 50 cells the filament became red hot, the inner side of the arch being hotter than the outer, after a while the arch bent over and broke on contact with the glass. He discontinued his experiments when it became impossible to progress due to difficulties in obtaining the vacuum and because of the expense of batteries. By 1877 thanks to the mercury vacuum pump invented by Sprengel in 1865 that could achieve a high vacuum together with cheaply generated power, Swan felt able to recommence his experiments. With the help of Sir William Crookes and C. H. Stearn in using the Sprengel pump he was quickly able to repeat his earlier experiments with greater success but now had to deal with the new problems of glass blackening and breaking of the carbon. He knew of people, such as the Russian Lodyguine, experimenting with Nitrogen filling but it did not occur to him to try it himself. During 1879 he and Stearn experimented with different filament materials and by 1880 had found that parchmentised cotton thread, made by treatment with sulphuric acid, was ideal. This filament was .01 of an inch in diameter and had the appearance and other properties of a metallic wire. It was strong and durable and it could be shaped into spirals as small as one tenth of an inch. He connected it to the lead-in wires by first thickening the ends which could then be crimped into sockets on the wires ends. Using this filament in a circular bulb with a two loop filament, he measured a light output of up to 60cp with 100 volts. In December 1880 using 40 of these lamps and a water powered Siemens generator he lit the home of a friend Sir William Armstrong at Cragside, Rothbury, now maintained by the National Trust.
Meanwhile Mawson & Swan marketed arc lighting equipment and probably manufactured some after 1878. It is possible that Swan did some development work with arc lighting.
In February 1881 and with 10,000 £10 shares, of which he held 25%, he set up a factory, Swan Electric Light Company Ltd. to manufacture and market his long straight sided light bulbs. The company was renamed Swans United Electric Light Company Ltd in May 1882. It had an increased capital of one million pounds. In 1883 they installed the lighting at the Law Courts in London. The light bulb was big business.
His cotton filament was not without problems. In particular it had to be made with the finest cotton thread as any variation in thickness would render it useless. To overcome this he found a method of removing the nitrous content and dissolving the remaining cellulose into a form that could be extruded into very fine threads. This material became known as ‘Tamodine’ and was used throughout the lamp industry by the end of the century. His process also started the development of man-made fibres.
After 1885 his research changed direction and he developed improved batteries and better copper conductors.
Swan died on the 27th May 1914 aged 85. On the 1st March 1979 Osram (G.E.C.) Ltd. produced a special bulb commemorating the centenary of Swans light bulb.
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