Alessandro Cruto

Alessandro Cruto was an Italian inventor, born in the town of Piossasco, near Turin, who created an early incandescent light bulb.

Son of a construction foreman, he attended the school of architecture at the University of Turin, while also attending Physics and Chemistry lectures with the dream of crystallizing carbon to obtain diamonds. In 1872 he opened a small workshop in his home village where he conducted tests on the production of pure carbon from ethylene. His efforts were rewarded in 1874 when his experiments succeeded in producing thin sheets of graphite, albeit his initial purpose was that of producing diamonds.

After attending some conferences held by Galileo Ferraris about the contemporary advances in electric technology – whose topics included Thomas Edison's experiments to find a suitable filament for incandescent lights – he discovered that a carbon filament treated with ethylene under high pressure and temperature acquired a positive resistance coefficient (its resistance depends on temperature; when temperature increases, it increases its resistance).

Cruto's filament is produced by deposition of graphite on thin platinum filaments in the presence of gaseous hydrocarbons. Sublimating this platinum at high temperatures leaves behind thin filaments of super-pure graphite.

He thought that his discovery could be used in incandescent lights instead of carbonized bamboo filament.

Helped by Naccari, he experimented with his invention in 1880 in the physics laboratory of the University of Turin.