Lye is a caustic, alkaline chemical that is useful for many purposes but also is hazardous. It can dissolve sticky substances such as fat and has a high degree of reactivity with other materials. Modern lye typically is the chemical sodium hydroxide, but potassium hydroxide was once the chemical compound that was commonly used. Whether in a flake, granular or liquid form, it is very dangerous and can cause damage to surfaces and people. Despite its hazardous nature, it is used in many common household products, such as laundry detergent and oven cleaner, and is even used to cure foods such as pretzels, green olives and mandarin oranges.
Sodium hydroxide is created using a chemical reaction between soda, or sodium carbonate, and calcium hydroxide, or lime. In raw form, it is made into solid flakes, chips or grains. Chemical suppliers provide sodium hydroxide to manufacturers for use in the making of a wide variety of products, such as fabric, paper, hand soap, metal polishers and drain de-cloggers.
Before the modern manufacture of lye, people were able to make it out of raw materials. For thousands of years, people have used types of lye for making soap and tanning hides. They burned certain hardwoods at a very high temperature to make white ashes. Water, mixed with a bit of baking soda, then was used to penetrate the ashes and remove the lye that they contained. When the ashes were filtered out, the water would hold enough lye for purposes such as dissolving the fat left on animal furs or mixing with other ingredients to make body soap.
This is one of many poisonous products that can be found in homes and that should be kept out of the reach of children and used only as directed. For example, a person should carefully follow the directions to clean sterling silver with a lye-based polish, because even the fumes can be dangerous. Lye-based products such as drain de-cloggers and paint stripper should never be used without proper air circulation.
Caustic lye products pose other dangers to surfaces. They can dissolve substances to the user's advantage, such as hair clogs in a shower drain, as well as to the user's detriment, such as the adjacent shower curtain. In fact, these products can damage and corrode paint, metal, cloth, plastic and especially skin. It can be so reactive that, in its solid form, it should be kept away from metals, such as aluminum, and the open air. It usually is non-combustible when dry, but it could ignite and cause a fire when mixed with water.