Question

The other day I dumped consumed tea leaves into a brass utensil because I needed the tea-pan urgently. The vessel with the tea leaves didn't get around for cleaning until the next day. Ergo, the tea leaves soaked overnight in dirty water. When finally the vessel was cleaned (as in hand-washed with utensil cleaner), the quality of shine was exceptional.

Piqued, I repeated the tea-soaking in another vessel — and was rewarded with the same high gleam. This vessel was made of aluminium.

Why do vessels get a better shine when tea-leaves are soaked overnight in it before washing?

Answer 1

The improved shine on brass and aluminium vessels after soaking in tea leaves is due to the complex formation between organic compounds in tea and metal ions, aiding in the removal of oxidation. Dishwashing liquids clean effectively because they contain surfactants that lower surface tension and help detach oils and dirt. The absence of surfactants when only water is used explains why an oily film remains in a salad bowl.

Step-by-step explanation:

The exceptional shine on brass and aluminium vessels after soaking tea leaves overnight can be attributed to the organic compounds in tea which can form complexes with the metal ions present on the surface of the vessels. These complexes may help in removing oxidation and other residues leading to a polished appearance. While dishwashing liquid is effective for cleaning, it requires surfactants to reduce surface tension and remove grease. Surfactants in dishwashing liquids also contain molecules that can bind to oils and debris, allowing water to wash them away. This is similar to the chemistry behind using tea leaves for shining metal surfaces. In the case of a salad bowl not properly cleaned with just water, the absence of a surfactant meant that the oily film remained since water alone cannot effectively remove oil due to the molecular structure of water and oil.