Chemically speaking, lye is an alkaline substance with a caustic reputation. Lye can harm surfaces that it comes into contact with when working with it, including your skin. In fact, dealing with it requires protective gear since it is so corrosive.

Sodium hydroxide is lye. It is available as liquid, flakes, or crystals. When soda (sodium carbonate) and lime (calcium hydroxide) combine and undergo a chemical reaction, sodium hydroxide results.

Caustic soda lye, also known as sodium hydroxide or lye, is an inorganic compound with a wide range of industrial uses: 

• Paper industry: Removes lignin and cleans bottles, pipework, and tanks 
• Food industry: Used in the production of potato starch and milk powder 
• Water treatment: Removes harmful metals like lead and copper from pools, regulates water's pH, and can be used to create sodium hypochlorite to disinfect water 
• Pharmaceuticals: Used in the manufacturing of blood thinners and cholesterol medication 
• Textile processing: Used in the production of textiles 
• Soap and detergent production: Used in the production of soaps and detergents 
• Organic chemicals: Used as an intermediate in the manufacture of organic chemicals like dyes, pigments, and agrochemicals 
• Inorganic chemicals: Used as an intermediate in the manufacture of inorganic chemicals including sulphites and phosphites
• Household products: Used in paint strippers and soaps 

Caustic soda is a strong base and alkali that can decompose lipids and proteins at room temperature and may cause severe chemical burns. When purchasing caustic soda or lye, you may need to sign a statement that you're not using it for illegal activities.