Cast-iron cookware
Because other cookware cleaning techniques like scouring or washing in a dishwasher can remove or damage the seasoning on a bare cast-iron pan, these pans should not be cleaned like most other cookware. Some chefs advocate never cleaning cast-iron pans at all; simply wiping them out after use, or washing them with hot water and a stiff brush. Others advocate washing with mild soap and water, and then re-applying a thin layer of fat or oil. A third approach is to scrub with coarse salt and a paper towel or clean rag.
Stone slab
Clothes were washed manually, by rubbing and sometimes striking them against a hard surface with soap. The aim was to do penetrate the mix of water and soap between the fibres of the fabric to pull-out the dirt. The slabs to wash the clothes were slabs of natural stone chosen to present a fine and relatively flat surface. The small rounded irregularities could help of friction in the washing process.