Lye safety for soap making: handling sodium hydroxide, PPE and first aid

TUREFF• •0

Sodium hydroxide, sold as lye or caustic soda, is what turns oils into soap. It is also a strongly corrosive chemical that can cause serious burns to skin and permanent damage to eyes. Thousands of people make soap safely at home, and they do it by treating lye with respect every single time. This guide covers the habits that keep you safe; it is not a recipe.

Know what you are handling

Sodium hydroxide usually comes as small white beads or flakes. It looks harmless, which is part of the danger.
It absorbs moisture from the air, so keep it in its original, clearly labelled, tightly sealed container.
Store it high up, out of reach of children and pets, away from food, and never in a drinks bottle or unlabelled jar.
Read the safety data sheet (SDS) for the product you buy. It sets out the hazards and the first aid advice for that exact product.

Personal protective equipment

Put all of this on before you open the container, and keep it on until everything is cleaned up:

Splash-proof safety goggles, not ordinary glasses. Eyes are the most vulnerable part of you.
Chemical-resistant gloves, such as nitrile, long enough to cover your wrists.
Long sleeves and long trousers, and closed shoes.
An apron is useful for protecting clothes.

Always add lye to water, never water to lye

Dissolving sodium hydroxide in water releases a lot of heat, very quickly; the solution can become hot enough to steam. The rule every soap maker learns is: add the lye to the water, slowly, never the other way round. If water is poured onto a pile of lye, the reaction can start in a small amount of liquid, overheat and spit or erupt out of the container, throwing hot caustic solution. Sprinkling lye gradually into the full amount of water, while stirring, lets the heat spread through the liquid. Other habits for mixing:

Use a container made of heat-resistant plastic marked PP (polypropylene) or HDPE, or stainless steel.
Never use aluminium: lye reacts with it and releases hydrogen gas. Avoid glass too, as repeated use with hot lye can weaken it.
Mix in a well-ventilated place, or by an open window, and turn your face away from the fumes rising off the solution in the first minute or so.
Use cold distilled water as your soap recipe directs.
Stand the container in a sink or on a stable, protected surface where it cannot be knocked over.
Leave the solution to cool uncovered and somewhere nobody will mistake it for a drink.

A safe workspace

No children, pets or distractions while lye is out. Do not walk away and leave it.
Clear the work surface completely and cover it with something you can wipe down.
Keep lye utensils for soap only, labelled.
Fresh soap batter and newly unmoulded soap are still caustic, so wear gloves when handling them for the first days.

First aid for splashes

Know this before you start, and keep the SDS nearby.

Eyes: flush immediately with plenty of clean, lukewarm running water for at least 15 minutes, holding the eyelids open. Remove contact lenses if it is easy to do. Get urgent medical help: call emergency services or go to A&E, and keep rinsing on the way if you can.
Skin: remove contaminated clothing and jewellery, then rinse the skin under plenty of running water for at least 15 minutes. Lye burns may not hurt straight away, so do not stop early because it feels fine. Seek medical advice for anything more than a tiny splash, and always for burns on the face or large areas.
Swallowed: do not make the person vomit. Rinse the mouth with water and get emergency medical help immediately.
Do not use vinegar or lemon juice on skin or eyes. Trying to neutralise a burn can create extra heat and damage. Water is the first aid; medical professionals take it from there.

Clean up

Wipe spilled beads up with a damp paper towel while gloved, then rinse the area well. Wash utensils while still wearing gloves and goggles. What safety habits do you follow when making soap? Share your setup and questions in the comments.