Matki, is the Hindi-Urdu word for an earthen

Earthenware

Earthenware is a common ceramic material, which is used extensively for pottery tableware and decorative objects.-Types of earthenware:Although body formulations vary between countries and even between individual makers, a generic composition is 25% ball clay, 28% kaolin, 32% quartz, and 15%...

 pot

Pot

Pot commonly refers to pottery, the ceramic ware made by pottersPot may also refer to:- Containers :* Plant pot or flower pot, a container in which plants are cultivated* Cooking pot, a stove-top cooking utensil* Chamber pot, a bedside urinal...

. It is used all over India

India

India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

, as well as Pakistan

Pakistan

Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...

, Bangladesh

Bangladesh

Bangladesh , officially the People's Republic of Bangladesh is a sovereign state located in South Asia. It is bordered by India on all sides except for a small border with Burma to the far southeast and by the Bay of Bengal to the south...

 and Sri Lanka

Sri Lanka

Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...

, as a home "water storage cooler". It has been in use since ancient times and can be found in houses of every class.

Cooling process

The cooling process works through evaporative cooling. Water seeps from mini-pores in the pot and evaporates, thus making the water inside cooler than the outside temperature. Hence it is used only during summers and not in winters.