was founded in 1905 by engineer and industrialist Sam Eyde as a fertilizer manufacturer. The first factory was opened at Notodden in 1907. Fertilizer factories need a lot of energy, making it beneficial to locate the plants near hydroelectric power plants. At Rjukan there was a large waterfall capable of supporting a hydroelectric plant. By 1911 Rjukan Salpeterfabrikk was opened. The Tinnsjø railway ferry service was opened in 1909 along with the Tinnoset Line and Rjukan Line. After the Thamshavn Line, these two lines were the second railway line in Norway to be electrified in 1911. The railway service used Telemark Canal until 1919 when the Bratsberg Line opened from Notodden to Skien. The railway was used both to transport raw materials to the factory and to transport the finished fertilizer to the harbour at Skien. There was also passenger trains that ran. In 1929 Norsk Hydro also establish itself at Herøya in Porsgrunn, and in 1991 the factory in Rjukan, and therefore also the railway line, was closed. The passenger trains, operated by Norges Statsbaner, had been discontinued already in 1970. In 1997 the ownership of the track was transferred to Stiftelsen Rjukanbanen, a foundation that started heritage operation of the line in 1999.
Ferries
The railway ferry service was provided by four different ships, SF Rjukanfoss, SF Hydro, SF Ammonia and MF Storegut. The three first were steam ships, and the latter two are still docked at Mæl. The service was the only ever railway ferry service on a lake in Norway, and D/F Ammonia is the only remaining railway ferry steam ship in the world.
SF ''Rjukanfos''
, built in 1909, was the first railway ferry on Lake Tinn. The steam ship was long and wide and 338 gross tonnes. It operated up to two daily departures each way, with a capacity of 120 passengers. The ship was rebuilt in 1946 to 648 gross tonnes but taken out of services and scrapped in 1969.
SF ''Hydro''
was the next ship to operate as railway ferry, entering service in 1914. It was slightly larger than Rjukanfoss, with , long and with two engines. On February 20, 1944 the ship was blown up by the Norwegian resistance movement at Lake Tinn's deepest point, with a load of heavy water onboard heading for Germany. It is believed that 18 people were killed while 29 survived the sabotage.
SF ''Ammonia''
In 1929 Norsk Hydro expanded their plant, and there was need for a third ferry. SF Ammonia was built the same year and was the largest of the three steam ships with 929 gross tonnes, two engines and a length of. It had a capacity of 250 passengers. From 1957 it was made a reserve ferry when Storegut was for service. It was taken out of service in 1991 when the railway closed, but can still be seen docked at Mæl. It is the only remaining steam powered railway ferry in the world.
MF ''Storegut''
is the last ferry and the only motor ship to operate on the lake. Built in 1956, it weighs 1119 gross tonnes, is long with three diesel engines. The passenger traffic with the ship terminated in 1985, and it was taken out of service in 1991 and is docked at Mæl.
