Why does salt cake at the bottom of ceramic jars?

Question

Noticed your salt caking at the bottom of a ceramic jar? Learn the potential reasons, from moisture to the properties of the container itself.

Answer 1

Salt cakes at the bottom of ceramic jars due to moisture absorption and subsequent recrystallization. The salt absorbs moisture from the air, dissolves slightly, and then recrystallizes as the water evaporates, forming a solid mass.

Detailed Explanation:

Salt, chemically known as sodium chloride (NaCl), is hygroscopic, meaning it readily absorbs moisture from its surroundings. Ceramic jars, while seemingly airtight, are often porous to some degree, allowing small amounts of humid air to penetrate. When this humid air enters the jar, the salt crystals on the surface absorb the moisture, causing a thin layer of the salt to dissolve.

As the moisture evaporates (which it will do, even in a seemingly closed container), the dissolved salt recrystallizes. This process of dissolving and recrystallizing happens repeatedly, especially at the bottom of the jar where gravity pulls the dissolved salt. Over time, these recrystallized salt crystals bind together, forming a solid, hardened mass or 'cake' at the bottom of the ceramic jar. The process is accelerated in humid environments.

Pro Tip:

To prevent salt from caking, add a few grains of uncooked rice to the salt jar. The rice will absorb excess moisture, helping to keep the salt dry and free-flowing.