How it began
Álvaro Alonso Barba was a Spanish priest, born in Lepe in 1569, who was sent to Peru in 1588 and combined parish work with the study of ores and mining. He lived in Tarabuco and Tiahuanaco, in present-day Bolivia, and in 1617 moved to Yotala, where he perfected his procedures for treating silver ore. The invention of the pan process, called cazo or fondo in Spanish, is dated to 1609 in Potosí. After 1624 he served the San Bernardo parish in Potosí, where the president of the Audiencia de Charcas asked him to write down the metallurgy of the district.
Before it existed
Silver ores were already treated with mercury before Barba, but the Dictionary of Scientific Biography notes that only Vannoccio Biringuccio had published an outline of a simple amalgamation process. Barba also recorded the smelting practice that local people had used before the Spanish arrived.
How it works
Barba carried out amalgamation over heat in copper vessels fitted with mechanical stirring devices. Ground ore was mixed with salt and mercury, and the mercury collected the silver. The Science Museum Group describes the key change as the use of copper vessels in place of iron. Barba stressed testing each kind of ore first to find the right kind and amount of additive, so that the mercury would gather the silver well. He also urged working out all costs, including fuel, mercury, equipment and labor, before starting.
How it spread
Barba dedicated his book, El arte de los metales, in 1637, and it was sent to Spain with the approval of the mayor and the Amalgamators Guild of Potosí. It was printed in Madrid in 1640 and went through about thirty editions in Spanish, English, German and French. The Science Museum Group records that Barba returned to Spain in 1657 and applied his methods at the silver deposits of Niebla in Huelva.
What lasted
El arte de los metales was the first significant treatise on metals written in Spanish, and the Dictionary of Scientific Biography calls it the only largely original treatise on the subject from the 17th century. Barba was among the first writers to argue for what amounts to laboratory control of a whole plant process. His methods were credited with a large share of the wealth of the province.
