Reasons why you should keep the salt bowl next to the window in winter

According to the US National Oceanic and Atmospheric Administration (NOAA), condensation does not depend on a specific temperature but on the difference between air temperature and dew point. Dew point is the temperature at which dew can form, when the air is saturated and cannot hold any more water vapor. Any further loss of heat will cause water vapor to condense. When water vapor in your home or car encounters a cold surface like a window, it turns into a liquid state, creating condensation.

There are many ways to deal with condensation, including placing a bowl of salt near a window during colder months. Andy Ellis, home and garden expert at Posh.co.uk, told the Mirror that salt has the natural ability to absorb moisture from the air. It will help dry the air, so when it comes in contact with the glass fewer condensation droplets will form. “This is a very easy, effortless tip. Just pour table salt or rock salt into a shallow bowl or small jar. The amount of salt used depends on the size of the window. In general, the larger the window the more salt you need, although usually a small bowl is enough,” according to Andy Ellis.

According to chemical engineer John Francis Richardson, a classic example of hygroscopicity is leaching, which occurs with many solids dissolved in water, including inorganic salts (e.g., calcium chloride). At a certain temperature, the vapor pressure of a saturated salt solution will be lower than that of pure water, and if it is less than the atmospheric partial pressure, moisture will be transferred to the solid surface, partly of them will dissolve to form a saturated solution. Once all the solids have dissolved, the process will continue until the partial pressure of the unsaturated solution equals the atmospheric pressure. In some cases, the formation of hydrates or higher hydrates of the salt may occur before the formation of the liquid phase. Liquids (e.g. sulfuric acid) may also be leachable.

However, according to the German Transport Information Service, salt only begins to absorb water vapor at high relative humidity. That is, at relative humidity up to 74% and 20°C, salt does not absorb a significant amount of water vapor. The critical water content of sodium chloride (NaCl) is 0.5% at 74% relative humidity. This is the melting point at which the salt begins to readily absorb water vapor and increases to the point that at 75% relative humidity, the salt will dissolve.