Technology or witchcraft: How does the clay filter work?

Temperatures are rising, but no more than the electricity bill at the end of the month. These may be some of the reasons why clay filters are fashionable and increasingly popular in stores. In addition to not using electricity to separate impurities from water, they keep the water fresh even at the height of the summer heat. But how is this possible?

The answer is physical. The upper part stores the water that will be filtered by the force of gravity slowly from drop to drop. With slowness and pressure, water passes through the porous walls of the filter, which can hold particles up to 1 micron (1 millionth of a meter), ensuring that most pollutants and bacteria do not descend into the lower compartment. This answer is easy to understand and even deduced. But what about the temperature?

According to Alexandre Veiga, professor of physics at the Marist Frei Rogério College, the clay that makes up the filter is mainly responsible for the thermal phenomenon. “The clay filter is made of clay, porous and permeable material, whose main characteristic is the exchange of heat with the external environment. The molecules that 'evaporate' absorb heat, and this heat exchange evaporation causes the water temperature to decrease, keeping it inside the ever-fresh clay filter, ”he explains.

Veiga explains that this also happens to the human body and cites our sweating, for example. "Just as the function of sweat evaporation is to lower the skin temperature, water evaporating from the filter lowers the water temperature." With this simple and economical mechanism, clay filters can keep water up to 5 ° C colder than room temperature.

The experts' recommendation is to avoid leaving the filter in direct sunlight as this would increase water evaporation and also keep it away from very humid places as this would make perspiration difficult. Otherwise, you can embrace the retro wave and cool off at your leisure.