Lye is dangerous stuff. If you’ve ever thought about making soap (or lutefisk, ew) but have been too scared, allow me to assuage your fears. If lye were a Ghostly Gondolier who haunts Venice, I would be the Scooby-Doo team who shows up to reveal that the boatman is really just an loser who wants to steal valuable medallions. By way of a clumsy metaphor, I’m trying to say that understanding what makes lye so scary can be a great way to face your fears.
Ever wondered why you don’t hear about lye burns very often? It’s because as long as you treat lye with a little bit of precaution, it’s easy to avoid injuries.
So let’s start: Lye. Sodium hydroxide. Caustic soda. All names for the same bad boy. Whatever you want to call it, it’s a strong base. Its pH is 14, which makes it even stronger than ammonia (which is often used in cleaning solutions) and is the alkali equivalent of hydrochloric acid (the stuff in your stomach that breaks down food). Lye is so intense that its usually marketed as a drain cleaner because it’s able to corrode all the stuff that normal cleaners can’t get.
Mixing lye with different chemicals leads to all kinds of reactions. Let’s take a look.
Lye + Water
NaOH(aq) + H2O(aq) → Na+ + OH- + H2O + heat
Mixing lye and water creates a very hot and strongly basic solution. This solution can not be undone.
Takeaway: When mixing lye and water, be careful! Coming into contact with a lye solution can give you both a chemical and a thermal burn. You should wear long rubber gloves and goggles to protect yourself from the alkali solution and from the heat. You should combine the two chemicals slowly and always pour lye into water and not the other way around. Why? Pouring water into lye creates a crust, trapping the chemical reaction below it. When the reaction gets too hot and too much pressure builds up, a “volcano” will occur and lye and water will erupt. An easy way to remember this is to think of snow falling on a lake.
Lye +(hydrochloric) Acid
NaOH + HCl → NaCl + H2O + heat
Mixing a strong acid with a strong base will neutralize it but will also give off lots of heat.
Takeaway: If your skin comes into contact with a lye solution, you shouldn’t pour vinegar directly on your skin as this can give you a thermal burn in addition to the chemical burn you’re already receiving. Instead, you should wash the area with water for 10-15 minutes to restore your skin to its normal pH (around 5.5 – slightly acidic) before using a weak acid to neutralize it. Additionally, as burns are highly susceptible to infection, you should only use distilled white vinegar (and not apple cider vinegar or lemon juice) as the fermented, acidic nature of some other acids can be ideal hosts for bacteria. Finally, you should use vinegar or a mixture of vinegar and water to clean your materials after you’re finished using lye.
Lye + Oil
C3H5 COOR COOR COOR + 3 NaOH + (H2O) →3NaCOOR + C3H3 OH OH OH
Mixing lye with oils gives you soap and glycerin.
Takeaway: While this is great for making soap, this is one of the reasons lye is so dangerous for your skin. Fatty tissues in and oil on your skin is exactly the kind of stuff lye likes to react with. Always wear long rubber gloves, goggles, and a mask to protect your skin, eyes, and mouth and call 911 if you come into contact with a significant amount of lye.
Lye + Aluminum
2 Al + 6 NaOH + x H2O → 3 H2 + 2 Na3AlO3 + x H2O
Mixing lye with aluminum gives off a flammable gas called hydrogen gas.
Takeaway: Never ever ever use aluminum bowls or materials when mixing lye. Not only do you risk creating a flammable gas, the lye solution can eat through your bowl, causing a lye solution spill. Use heavy plastic or stainless steel instead.
+ + +
- Work in a well-ventilated space
- Wear long rubber gloves, goggles, and a breathing mask
- Never use aluminum tools
- Mix in stainless steel or heavy plastic bowls. If you use plastic, test the strength of the container by boiling water (just water, no lye) and pouring it in the container. If the plastic holds up, you’re safe.
- Use a bowl large enough to contain splashes
- Always pour lye into water and lye solution into oils to avoid volcanoes. Think “snow falling onto a lake.”
- Always buy 100% sodium hydroxide from a reputable supplier. Don’t substitute lye for a drain cleaner as it may have extra ingredients
- Store lye in containers marked “poison” away from children, animals, and unsuspecting adults
- After using lye, clean your materials and workspace with plenty of water, soap, and distilled white vinegar
- If swallowed, rinse mouth with water and drink one or two glasses of water. Do not induce vomiting. Call poison control (1-800-222-1222) or 911
- If lye comes in contact with your eyes, immediately flush your eyes with water. Remove any contact lenses and continue to flush eyes with water for at least 20 minutes. Call poison control (1-800-222-1222) or 911
- If lye comes in contact with your skin, gently wipe it off and remove any contaminated clothing. Flush your skin with plenty of water for at least 15 minutes and then wash thoroughly with soap and water. Contact a doctor, poison control (1-800-222-1222) or 911 if the burn is large