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Lye Safety

Originally published in HSMG Journal of Winter 2005-2006

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.

Lye Transportation and Shipping

For shipping lye, the primary governing body is the US Department of Transportation. According to the Federal Regulations (CFR49, Chapter 1, Parts 172 and 173) potassium hydroxide and sodium hydroxide are both classed as “Corrosive” and have limitations on the amount of product that can be shipped, how it must be labeled and how it can be transported.

Lye packaged and shipped as a “consumer commodity” must meet very stringent requirements but does not require a HazMat handling fee. The Boyer Corporation offers a specially packaged case containing twelve (12) 2lb cans which is accepted by UPS without HazMat fees. Larger (“bulk”) shipments always require special hazmat labeling and fees imposed by the carrier.

No lye shipment, large or small, can go by air transport; it’s ground shipment only. So don’t order at the last minute hoping for overnight delivery.

Although these regulations can be somewhat restricting, keep them in mind when ordering your lye. Don’t expect or request that your vendor violate the law.

If you purchase lye from a vendor and transport it yourself, be safe! While an accident is unlikely, you wouldn’t want to add lye burns to the list of injuries. Use your common sense. Don’t carry bags of lye in the passenger portion of you vehicle (ESPECIALLY if you have children with you) and make sure any lye containers have labels that would be clearly visible to rescue personnel. Also keep in mind that if a HazMat team has to be called the cost could be in the thousands of dollars. Check your auto insurance policy to make sure it’s not void if you are transporting a caustic substance or other hazardous materials.

Lye Storage

Once you get your lye, make sure you have it safely stored. Remember, it has to be safe for you AND for others who may come in contact with it.

First of all, don’t advertise that you have lye on the premises any more than you have to. As Meth cooks are less and less able to get what they need, they are more likely to resort to illegal means to get their supplies. Several soapmakers have reported that their buildings were broken into and lye stolen.

Store lye someplace that is not easily accessible, such as a locked cabinet or storage area. Put the lye in a rigid container, seal it tightly and clearly label the container. Post basic lye first aid procedures on the container and also visible nearby in case someone does get exposed it. If firefighters or rescue personnel are called to your home or building for any reason, inform them there is lye present.

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).

First Aid for Lye

In the event of contact use recommended first aid procedures:

  • 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.

Lye Safety Guide

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

Safety and Hazard Summary


Not combustible. Contact with moisture or water may generate sufficient heat to ignite combustible substances. In case of fire in the area, all extinguishing agents are allowed.


Symptoms: Corrosive. Burning sensation. Sore throat. Cough. Labored breathing. Shortness of breath. Symptoms may be delayed.
Prevention: Local exhaust or breathing protection.
First Aid: Fresh air, rest. Half-upright position. Artificial respiration if indicated. Refer for medical attention.


Symptoms: Corrosive. Redness. Pain. Serious skin burns. Blisters.
Prevention: Protective gloves. Protective clothing.
First Aid: Remove contaminated clothes. Rinse skin with plenty of water or shower. Refer for medical attention.


Symptoms: Corrosive. Redness. Pain. Blurred vision. Severe burns.
Prevention: Face shield, or eye protection in combination with breathing protection if powder.
First Aid: First rinse with plenty of water for several minutes (remove contact lenses if easily possible), then take to a doctor.


Symptoms: Corrosive. Burning sensation. Abdominal pain. Shock or collapse.
Prevention: Do not eat, drink, or smoke during work.
First Aid: Rinse mouth. Do NOT induce vomiting. Give plenty of water to drink. Refer for medical attention.


Sweep spilled substance into suitable containers. Wash away remainder with plenty of water. (Extra personal protection: complete protective clothing including self-contained breathing apparatus).


Store away from strong acids, metals, food and feedstuffs. Keep dry. Well closed. Store in an area with corrosion resistant concrete floor.


Use unbreakable packaging; Put breakable packaging into closed unbreakable container. Do not transport with food and feedstuffs.
Hazard Class 8; Packing Group II

Print this page and post in any area where sodium hydroxide is stored or used.

Sodium or Potassium Hydroxide — Additional Information

Chemical Dangers

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).

Occupational Exposure Limits:

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)

Inhalation Risk:

Evaporation at 20°C (68°F)is negligible; however a harmful concentration of airborne particles can be reached quickly.

Effects of Short-Term Exposure:

Corrosive. The substance is very corrosive to the eyes, the skin and the respiratory tract.

Corrosive on ingestion. Inhalation of an aerosol of the substance may cause lung edema (see Notes).

Effects of Long-Term or Repeated Exposure:

Repeated or prolonged contact with skin may cause dermatitis.

Environmental Data:

This substance may be hazardous to the environment; special attention should be given to water organisms.


The applying occupational exposure limit value should not be exceeded during any part of the working exposure. The symptoms of lung edema often do not become manifest until a few hours have passed and they are aggravated by physical effort. Rest and medical observation are therefore essential. NEVER pour water into this substance; when dissolving or diluting always add it slowly to the water.


The information herein was compiled from data found on the OSHA and NIOSH websites, and specifically the International Chemical Safety Cards (produced by the International Programme on Chemical Safety) and the NIOSH Pocket Guides to Chemical Hazards for Sodium Hydroxide and Potassium Hydroxide. OSHA, NIOSH and the IPCS acknowledge that their information may not reflect all the detailed requirements included in national legislation on the subject and that the user should verify compliance with the relevant legislation in the country of use.

The Handcrafted Soap & Cosmetic Guild, Inc. is providing this summary of available information as an educational tool on the use and handling of lye during the soap making process. The HSCG strongly recommends that any soapmaker using sodium or potassium hydroxide become throroughly familiar with all safety recommendations and any local, county, state or federal regulations governing the use, stroage and/or transportation of sodium hydroxide or potassium hydroxide.

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