Faraday's gold films, four on watch glasses

One of Faraday’s last chemical investigations was on the preparation of thin metal films. The results were presented as the Bakerian lecture for 1857, ‘Experimental Relations of Gold (and other Metals) to Light’.

Faraday produced thin gold films either by evaporating a drop of gold chloride solution on a watch glass and then heating it, or reducing the solution on the glass with the vapour of phosphorus dissolved in carbon disulphide. It was noted that by reflection of light, gold films had the usual yellow metallic lustre, but by transmitted light, the films appeared red of purple.

Faraday shower that rays of light passing through the gold films were polarized.