The Fundació Miró in Barcelona preserves the only source of mercury in the world, the work of the American sculptor Alexander Calder. The fountain was part of the Pavilion of the Republic at the Universal Exhibition in Paris in 1937. Calder donated it to the museum of his friend Joan Miró in 1975 and, since June 1990, it can be seen working thanks to the mercury from the Almaden mine, the same origin of the one that ran through the fountain exhibited in the French capital.
Calder's famous mobile sculpture was in 1937 next to Picasso's Guernica. It was conceived as a tribute to the town of Almaden, in Ciudad Real, which produced 60% of the world's mercury. Its inclusion in the pavilion, in the middle of the civil war, was interpreted as a resistance to fascism. Almaden remained in the Republican zone and mercury was one of the raw materials coveted by Nazi Germany, Franco's ally in the war.
The toxicity of mercury means that currently its exhibition at the Fundació Miró takes place totally isolated from the public, inside a completely closed glass cabin that was built in 1988 for that purpose. The mercury that currently flows through the source was also donated to the Fundació by the management of the Almaden mine. According to Ramon González, the museum's infrastructure manager, there are 268 liters, plus 80 stored, with which the level of the fountain can be maintained for the next 70 years. Every two years a level control is carried out, since the mercury volatilizes above 21 degrees.
Therefore, the temperature of mercury is maintained at 17.4 degrees. A specialized company is responsible for the periodic maintenance and collection of the mercury that ends up outside its tank due to small and continuous splashes. González adds that it is planned to replace the current pumping system with an "eccentric pump", which will prevent the dripping and heating of the mercury, which in turn will increase the longevity of the source.
Calder was the only foreign artist invited to the Republic Pavilion, the work of the architects Josep Lluis Sert —also the designer of the Fundació Miró building on Montjuïc— and Luis Lacasa. The pavilion was rebuilt in the Vall d'Hebron area for the 1992 Olympic Games.
