Ceramics of indigenous peoples of the Americas
The clay body is a necessary component of pottery. Clay must be mined and purified in an often laborious process, and certain tribes have ceremonial protocols to gathering clay. Different tribes have different processes for processing clay, which can include drying in the sun, soaking in water for days, and repeatedly running through a screen or sieve. Acoma and other Pueblo pottery traditionally pound dry clay into a powder and then remove impurities by hand, then running the dry powder through a screen, mixing it with a dry temper, and then mixing water to create a plastic paste. In preparing the clay, potters spend hours wedging it to remove air pockets and humidity that could easily cause it to explode during firing. The clay then needs to "cure" over time.
Slate industry in Wales
In Blaenau Ffestiniog, the Llechwedd Slate Caverns have been converted into a visitor attraction. Visitors can travel on the Miners' Tramway or descend into the Deep Mine, via a funicular railway which uses an old incline, to explore this former slate mine and learn how slate was extracted and processed and about the lives of the miners. The Deep Mine, opened in 1979, is accessed by Britain's steepest passenger railway, with a gradient of 1:1.8 or 30°. In the chambers, formed by slate extraction, sound and light is used to tell the story of the mine and mining. The Braichgoch slate mines at Corris have been converted into a tourist attraction named "King Arthur's Labyrinth" where visitors are taken underground by boat along a subterranean river. They then walk through the caverns to see audiovisual presentations of the Arthurian legends and stories from the Mabinogion and the tales of Taliesin. The Llwyngwern slate quarry near Machynlleth is now the site of the Centre for Alternative Technology. A number of the railways which carried the slates to the ports have been restored as tourist attractions, for example the Ffestiniog Railway and the Talyllyn Railway.