Charles Martin Hall. Portrait of Charles Martin Hall (1863-1914), American chemist. Hall invented a cheap, electrolytic process for making aluminium in 1886 at home when aged only twenty- two. The technique involved dissolving aluminium oxide in molten cryolite, and passing an electric current through it using carbon electrodes. A French metallurgist, P.L.T. Heroult, independently devised the same technique in the same year. The technique is now called the Hall-Heroult process. It allowed aluminium to be made cheaply for the first time since it was initially isolated in 1825. Both inventors were also born and died in the same years as each other.