The substance is a strong base, it reacts violently with acid and is corrosive in moist air to metals like zinc, aluminium, tin and lead, forming hydrogen, a combustible/explosive gas. Reacts with ammonium salts to produce ammonia, causing fire hazard. Attacks some forms of plastics, rubber or coatings. Rapidly absorbs carbon dioxide and water from air. Contact with moisture or water may generate heat (see Notes).
OSHA Permissible Exposure Limit: 2 mg/m3 (TWA: Time weighted average) NIOSH Recommended Exposure Limit: 2 mg/m3 Ceiling (15 minutes) NIOSH Immediately Dangerous to Life or Health : 10 mg/m3 (2 mg/m3 signifies contamination of 2 miligrams per 1 cubic meter)
Evaporation at 20°C (68°F)is negligible; however a harmful concentration of airborne particles can be reached quickly.
First Aid for Lye
- Eyes: Immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper eyelids. Get medical attention immediately.
- Skin: Immediately flush the contaminated skin with water. Where there is evidence of skin irritation, get medical attention.
- Difficulty breathing: Get respiratory support.
- Ingestion: Rinse mouth. Do NOT induce vomiting. Give plenty of water to drink. Get medical attention immediately.
An interesting note on the safety of lye is that the lowest published human lethal oral dose is 1.57 mg/kg of body weight. That would be 78.5 mg (less than .1 grams) for a person weighing 110 lbs. However sodium hydroxide is listed among FDA’s “direct food substances affirmed as generally recognized as safe” (GRAS) when used in foods at levels not to exceed “current good manufacturing practice”. Lye is used, for example, in making black olives!
The bottom line? BE SAFE – for yourself and the people around you.
Sodium Hydroxide Also known as Caustic soda, Sodium hydrate, Soda lye, NaOH Molecular mass: 40.0; CAS# 1310-73-2
Potassium Hydroxide Also known as Caustic potash, Potassium hydrate, Potassium lye, KOH Molecular mass: 56.1; CAS# 1310-58-3
Lye Safety and Handling
Soapmakers accustomed to using lye are familiar with the safety precautions that should be taken and the basic first aid to be applied. But, just to reiterate:
- Prevent skin contact (use gloves and long sleeves)
- Prevent eye contact (goggles or face shield)
- Wash skin immediately when contaminated
- Remove contaminated clothing immediately
- Have eyewash and quick drench available
- ALWAYS add the lye to water (not water to lye).
Sodium Hydroxide (Caustic Soda/Lye) and Potential Occupational Exposure Risks
FAQ
Can you just buy lye?
What is lye used for in murders?
Is it OK to touch lye?
Is lye OK to use?
Is caustic soda a lye?
Commercially available caustic soda or sodium hydroxide is usually sodium hydroxide monohydrate, NaOH·H 2 O. Caustic soda is one of the common names for sodium hydroxide (NaOH). It is also known as lye, although lye may refer to either potassium hydroxide or sodium hydroxide. Pure caustic soda is sold for making candles or soap.
What is a lye hydroxide?
A lye is an alkali metal hydroxide. Traditionally it was obtained by using rainwater to leach wood ashes, which are strongly alkaline and highly soluble in water, of their potassium hydroxide (KOH), producing lye water, a caustic basic solution.
Is Lye safe?
The answer is— Yes! Lye is often times a misunderstood ingredient. However, once it undergoes a chemical reaction to become soap, it’s completely safe.
Is Lye a hazardous material?
We all know that lye is a hazardous material. Since we use it safely every day, it may not seem so hazardous to us. But consider the poor UPS driver or postal employee that has to handle a box containing a broken lye container or the firefighter that sprays water on a bag of lye in the course of putting out a fire.