The company began to diversify after the First World War. Underpinning this change was a new emphasis on industrial research and external alliances.
World War I pushed up food prices to staggering heights, and working people on ordinary wages went short. In Notodden, the situation became so serious that many people wouldn't have survived the war years without the bread coupons from Hydro.
Hydro gradually built up a research environment focusing on developing new industrial processes and improving fertilizer technology. From 1919, Hydro's main research centre was at Skøyen in Oslo and was led by Birger Fjeld Halvorsen.
One is large and quite grand, another is a charming country house, a third is a picturesque lighthouse. Hydro's guest houses have their own stories to tell from the company's history.
Herøya, near Porgsrunn is where the Tinnelv river that flows through Rjukan and Notodden meets the Oslo fjord.