How water in Earthen Pots get chilled?

Earthen pot made out of clay.

Summer is almost there, a few weeks and summer will knock the doors. considering sunny days, nowadays everyone is busy to buy a Matka/ Earthen Pot. It is the most economical and healthy way to drink chilled water. But ever wondered how a single piece of clay can chill the water when it's hot sunny days out there?

In this topic, we gonna see how this happens.

First of all, let's understand how a Matka/earthen pot is manufactured. Potter takes some clay and molds it into the desired shape on spinning wheel. Then he bakes it into the furnace and finally, we get that reddish, rounded Matka or Earthen Pot.

basically, any utensil made up of clay is porous in construction. similarly, Matka/ earthen pot is also porous, but we can't see porosity with naked eyes. porosity is the main reason behind the cooling process of water in it.

let's see how it happens,

Heat transfer process takes place.

Whenever we pour water into it, after a prolonged period of time water is absorbed by its walls. this happens due to capillary action. porosity present in wall acts as a capillary tube and absorbs fluid that is water. water is oozed to the outer surface of the walls.

The outer surface of the wall is continuously exposed to the open atmosphere. water present on the wall's surface requires some amount of energy in terms of heat to evaporate and mix with atmospheric air. Now what happens, As water requires the amount of energy to get evaporate, water takes heat from fluid present inside the walls that is water itself.

So the overall process is that heat from inside water is absorbed by surface water, this water gets evaporated. again some amount of water oozes out, absorbs heat gets evaporate. This process continues for a long period of time, and finally, we get chilled water. 

Interesting isn't it? This how a simple Matka/earthen pot serves chilled water and a complex physics plays a role behind the scene.