Method of isolating silver from its ore, apparently dating from pre-Columbian times. The ore was crushed and ground by mule power in arrastras, reducing it to a fine mud. This was then spread over a courtyard or patio, sprinkled with mercury, salt, and copper sulfate, and mixed by driving mules over it. Chemical reactions caused the silver to dissolve in the mercury. When the amalgamation was complete, the material was agitated with water in large tubs and the mud run off. The amalgam at the bottom was collected and heated to drive off the mercury. Used for much of the world's silver production for 350 years, the process was replaced by the cyanide process early in the 20th century.
Learn more about patio process with a free trial on Britannica.com.
In Spanish and Latin American architecture, a courtyard open to the sky within a building. A Spanish development of the Roman atrium, it is comparable to the Italian cortile but provides more seclusion, possibly due to Moorish custom. The patio of the contemporary U.S. house is a paved outdoor area adjoining or partially enclosed by the building and often used for outdoor dining.
Learn more about patio with a free trial on Britannica.com.
Patios are typically made of concrete or stone slabs laid over a firm base. This base is often formed of a layer of compacted hardcore (stone chips), a layer of sharp sand, and a layer of cement mortar. The firmness and stability of the base is essential to the robustness of the top layer of slabs - an infirm base will typically result in cracked slabs. Patios that hold a lot of weight, such as driveways, require stronger foundations than those that are designed for light use.