Videos showing the process of creating various items, including decorative pieces and ironware, frequently appear on social media. These videos are very popular and gain many views. However, in some of these videos, it can be observed that workers use lemons, onions, or tomatoes after shaping the iron products.
People are interested in why this is done and what the reason for workers using onions and lemons is. The essence of this process lies in science. After shaping the metal, it needs to be hardened to give it strength; this process is called quenching.
The method of cooling iron is very important. Some iron products with sharp edges cannot simply be dipped in water. Before immersing them in water, they are first removed from the moist substance. If very hot metal is thrown directly into cold water, cracks can appear in the metal due to thermal shock.
Tomatoes or lemons contain thick pulp and water, which allow the metal to cool more slowly and controllably compared to water, preventing brittleness. Therefore, people use tomatoes, lemons, ginger, banana stems, dirt, or damp soil for this purpose. Since tomatoes and lemons contain a lot of water, upon contact with very hot metal, the water quickly turns into steam, and the surface of the metal cools rapidly.