Joseph Swan

Mar 21, 2021

When we think of the invention of the lightbulb, we think of Thomas Edison. But like any scientific discovery, the final product only culminates after years of research by multiple scientists. In the late-19th century, many bright inventors pushed themselves to find an alternative to gas lamps and burners, searching for electrical alternatives like the incandescent light bulb or the arc lamp. One of these inventors was Sir Joseph Swan. He was born in 1828 in Sunderland to a family of ironmongers with five siblings. His family money enabled him to attend school and undertake an apprenticeship in pharmacy, before abandoning the practice and moving on to manufacturing chemicals.

Sir Joseph Swan

Sir Swan’s contribution in the field of lighting was mostly improving and commercializing the efforts of his predecessors. The voltaic pile invented by Alessandro Volta consisted of copper wire that would emit light when current passed through it. Humphrey Davy came up with an alternate model that used charcoal electrodes and a carbon rod filament. Davy’s filament was then replaced by platinum by Warren de la Rue. Swan began his experiments from this point in time, suggesting that the expensive platinum should be replaced by carbonized paper filaments. His experiments revealed that carbon filaments have a negative temperature coefficient of resistance(α) which meant that the hotter it got the more its resistance would decrease. Thus, a slight increase in the voltage supply would heat up the material quickly and enable it to draw more current. His initial prototype included this principle as well as a vacuum pump to limit the air reaching the filament. However, he was limited by the vacuum pump technology of his time and couldn’t create a practical model to manufacture. He first presented a working model to the Newcastle Chemical Society on December 18, 1878.

Swan's incandescent light bulb

After registering for a patent, he went on to start his own lighting business, the Swan Electric Light Company. His house was the first in the world to have lights installed and subsequently many areas in London started to use Swan’s lightbulb. With advances in lightbulb technologies by his contemporaries, his model and patent kept being updated. This was a point of conflict between his competitor Thomas Edison of the Edison Illuminating Company in the USA. He alleged that Swan had stolen his design of the filament and claiming it as his own, sued the Swan Electric Light Company for copyright infringement. Due to Swan’s strong patent claims and prior research and demonstration in the field, he had a strong legal defence but both parties agreed to have a merger to form the Edison & Swan (Ediswan) Light Company in order to avoid unnecessary fees and expenses against legal actions and fair usage. They sold lightbulbs almost identical to that of Swan’s, with the exception of the filament. Thus, it is unfair to declare Thomas Edison as the sole inventor of the lightbulb and Swan’s contributions must not be forgotten.

A catalogue of the Ediswan Light Company

Other than his innovations in the world of lighting technology, his research helped advance photography technologies as well. His experiments with heating materials to reduce their resistance led him to discover that heating a silver bromide emulsion increased its sensitivity, and could be used for photographic prints. This paper is used even in modern black and white photographic films. With progress in his study, he improved his method of exposure by developing carbon prints using a carbon tissue. The emulsion is applied to a paper and exposed to light from a film. The sensitivity of the emulsion makes it so that it hardens proportional to the amount of light it receives. Thus, an image can be formed on the paper through varying hardness of the spots that make them proportionally darker.

Carbon tissue in image development

Sir Swan's case is illustrative of the condition of many other scientists, whose important contributions are over-shadowed by those of their peers who are more visible in the public eye. Hopefully, this article was able to illuminate a bit more the figure who helped bring the light into our lives.

An article by Rahul Tripathy

Disclaimer: the pictures in the article are for illustration purpose only. Neither the writer nor PHoEnix has a claim over them.

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