Lime, also called quicklime or white lime, is a common material used in many ways. In Pakistan, people still make it the old way by heating limestone in clay kilns to about 900 °C for two days. The heat changes limestone into quicklime. When quicklime touches water, it reacts strongly, gets hot, and turns into slaked lime. Lime is not only for building houses—it can clean fish ponds, balance water pH, protect trees from insects when painted on their trunks, and is even used in making century egg