Soaping with Lye – Chemical Safety in the Kitchen

Working with lye in the kitchen is what will separate your soap making projects from every other bath & body product you create.  Lye is one of the cardinal ingredients need to turn oils into soap. It is a short nickname for either one of two chemicals Sodium Hydroxide or Potassium Hydroxide. Sodium hydroxide is used for bar soap while Potassium Hydroxide is used when the result is for liquid soap. In this article we will give you most of the details you need to know about working with lye.

If you’re new to soap making we recommend you read our  – How to Make Soap: The Basic Basics – article. If you are looking for more resources in soap making including full tutorials and printable recipes then join us in the Learning Library, registration is free and there is a ton of free instruction.

Safety Check

You can seriously hurt yourself or others by making soap if you do not get into the habit of practicing safety.

Do you remember how unnecessary it felt when you filed into the science lab room in high school on the day everyone was dissecting the frog, and no one was allowed to cross the white line until everyone had their safety glasses on? You looked like a nerd. It messed up your well-sprayed hair. Your glasses fogged up so you couldn’t see, all because some old teacher wanted you to believe that you needed eye protection, because somehow by cutting into a frog belly somebody’s scalpel might end up in your eye. Remember how ridiculous and over precautions that felt? Yeah…..soap making is not like that. You really need to wear your glasses.

Making soap in your kitchen is not like making a benign science class volcano. You must practice safety standards every time. You can get hurt, or worse, you can accidentally  hurt your children.

Now, before we begin with the safety information that you need, let’s say you get into the swing of soap making and you have your system down pat. Your supplies are locked up. You have a space that pets and kids aren’t running through. You’ve got the hang of making your cold process batter down. You don’t really need to throw on an apron or gloves, or glasses, and you’re ready to go.


Go get your safety glasses, pull out your plastic gloves. Put on a long sleeve shirt, yes, button it up. Wear long pants. Wear socks. Do it. Do not skip out on this step for the following reasons.

  1. You are maintaining the habit. If you start slacking off on safety habits it’s a slippery slope, and if you never have a splash of activated lye touch your skin that’s great. Eventually, you will get a little too confident, and you’ll find yourself whipping up a bowl of soap like its pancake batter at the end of one elbow while wearing a tee shirt, shorts, and flipflops and making your eggs for lunch at the end of your other elbow. Fine. It’s all good, till the day comes that you flip that first bowl, and it spills on your arms and knees. We’ll discuss chemical burns in a moment.

  2. You are setting a precedent for everybody who might be watching you. Let’s say you’re a soap making ninja, and there’s no chance of an accident in your world ever, period, end of story. Let’s say you have more than one teenager living in your house. The odds are now increasing that one of them is a knucklehead. Don’t be offended. All teenagers seem to waft in and out of the knucklehead part of the brain at some time or another. Kids will do what you do, not what you say, always, er mostly, hopefully. Do you want to risk it? A lax attitude on safety in front of the ones who look up to you is a bad habit. This goes for texting while driving, smoking, throwing aerosol cans in fire pits, running with scissors, you get the idea. That’s what your science teacher was doing when you had to wear those stupid glasses to dissect a frog, by the way.

  3. Do not prepare food on any surface where you are making soap. Do not make soap over the dirty dishes in your sink. We’ll get to chemical burns in a minute, but if you don’t want chemical burns on your hands and face, (and you don’t) you sure as blazes don’t want in your mouth and throat, or god forbid stomach.

What is a chemical burn?

One of the main ingredients you use to make soap is lye. Depending on the type of soap you make, you will be using Sodium Hydroxide or Potassium Hydroxide. Mostly you will be working with Sodium Hydroxide, labeled NAOH. Sodium hydroxide is caustic. When storing Lye for soap making it will be in a white crystalline form in an air tight bottle. Touching these crystals will not hurt you until they have been activated by moisture or water.

Once mixed with water, it becomes activated lye. The water temperature will heat and even boil. Getting this on you can result in deep tissue burns. It takes almost nothing but a tiny spatter in your eye to result in blindness. What a shame it would be to lose one’s eyesight over not pulling those stupid glasses over one’s face in their own kitchen.

Quenching a chemical burn is not the same as a burn from a hot pan or sipping your tea when it’s too hot. Once the chemical makes contact it won’t just stop burning if you run it under cold water. There’s a chance it will keep burning down into the tissue for several minutes after you have stopped, wiped it off, and are standing under the sink.

Keep Lye Out of Reach of Pets and Children. There is no treatment for the consumption of Lye. Once it is in the digestive tract, your emergency care team will try to keep you as comfortable as they can. That is bad.

Another way lye can be dangerous is through inhalation. Sodium Hydroxide is a respiratory irritant. When making your lye solution, you will have your measured amount in a bowl and you will slowly add water. (You will always add the lye to the water, not the other way around) I always have this bowl sitting in the bottom of my sink to contain any possible splash. You will stir the crystals, and you will see a white gas disperse from the top of the solution while you feel the temperature rise quickly against your hand. At this moment, it will occur to you to step away because after the third warm breath of lye vapor you will be choking and feeling a burn in your chest. Of course, this doesn’t apply to you because you always wear your white mask. This applies to the knucklehead who skipped this chapter and had to try it once to figure out the mask is a must.

It’s also possible that the fumes don’t bother you too much, but they are only noticeable enough for you to open a window and move your head out of the way. For someone who is making a batch of soap regularly, this will irritate your lungs eventually, and it can increase the chance of respiratory infections.

These potential disasters are entirely preventable with good habits, and common sense.

Now that I’ve properly terrified you about making soap. Let’s get Started

First you’ll need to order your lye. You can get your Sodium Hydroxide Here

I like to buy lye with a locking child safety top in a bottle compared to the bag. One reason is that with a locking cap the crystals are less likely to be in constant contact with the air and humidity. An open bag can result in the top layers of the lye that starts to become neutralized and that will slightly mess up your measurements. This isn’t a big deal, but if you store your lye for a long time you will notice some differences.

Everything about Lye

Lye Is the reason for all the safety precautions. By now you’ve gotten the feeling that we don’t play around with this stuff. Anytime you pull out the lye, you need to be thinking sensibly about your surroundings and accident prevention. In soap making there are two types of lye:

Sodium Hydroxide: Often seen written as NaOH is the most common form of lye in soap making. This is the chemical that you want when you are making your hard bars of soap. Some will give you instructions to go to your local Home Depot and look for it in the aisles with drain cleaner. I have never been able to find it this way, and to this day don’t know of any place that sells 100% Lye as drain cleaner. I have, however, been told that it is still sold this way in Canada.

For soap making purposes you want to buy this from a soap supply store online. It will be pure and labeled food grade. Lye is a hazardous chemical and mush be shipped in an appropriate way. Your supply store should know how to do this, and make sure that you follow any regulations in your state about acquiring lye. This is a chemical that has been known to be used to make drugs. The lye you purchase will likely be in the form of dry white crystals in lock tight containers.

Storing lye must be handled as carefully as using lye. Make sure your lye is in a locked, dry, safe cupboard, or room. Lye becomes active with water, so humidity is your enemy. I keep my bottles of lye locked in cabinets on shelves close to the ground. There is zero chance of getting knocked off a shelf and spilled on any kitchen counter tops.

Never, never eat, snack, or prepare food when your lye is open, out, or if you are making soap. When you are soaping you are not eating or drinking. When you are eating or preparing food, your lye is locked out of sight and surfaces have been well washed down.

Potassium Hydroxide: This is often seen written as KOH and is the chemical used to make liquid soap. You may start off making bars of soap first and won’t need to buy the potassium hydroxide until you are ready to get your feet wet with another project. The most important thing about KOH is that it is NOT NaOH. These two chemicals cannot be switched out and substituted in each other’s recipes. This chemical is also caustic and must be used and stored with the same care.

How exactly is lye used?

Lye will be combined with your oils while you are working on your recipe. When the lye and the oils are mixed they combine chemically and create something completely different, soap. This process is called saponification. This is where the molecules are completely rearranged and you end up with neither lye nor oil when all the molecules have combined.

The most important thing you need to know about this chemistry is that the amount of lye to oil is a specific calculation. Each oil has a different saponification value and you will need to run your recipes through a lye calculator when crating your own recipes. You cannot just throw lye and oil together or you could end up with a mess.

Lye must be dissolved into water

Before you add your lye to your oils you will need to dissolve it in water. The recipe from your lye calculator will also have given your water ratio. After carefully measuring theses you will add them together and dissolve the lye into a solution. What you must know is that lye is very, very reactive and volatile. Even when you do everything correctly you will get a big chemical reaction. First, make sure your water is cold. This will help greatly. Second, always pour your lye crystals into the water, not the other way around. This keeps your reaction from getting out of control. You will notice steam and heat immediately. Your water may bubble and you can feel the heat coming off the reaction. Keep your face away. Don’t breathe the steam. Make sure you are near a ventilated area and have your mask on. You might get a whiff of steam in your lungs and it will make you cough and step back. Try not to let this happen. Over time this can cause damage. Take care of yourself in these little increments as you go along. You are only serving yourself in the long run. Once you have stirred your ingredients into a solution leave the water alone to cool down. Make sure your lye water is out of the way so you don’t bump into it as you are working. I always work on my counter top with the lye water in a bowl at the bottom of my clean sink. This way it is kept safe in a low place with no risk of knocking it off the counter.

How do I calculate how much lye I need?

The easiest way to calculate how much lye you need is to go online and search for a soap calculator. This will allow for you to put in your recipe and the oil amounts and click a button with a quick tally of the amount of lye and water you will use. A great resource is There is a way to do the math by hand if you’re one of those people who like to work things out with a pencil and paper. Here is a chart with the saponification value of the common oils used in this book and an example on how to calculate your lye. The saponification values here are for Sodium Hydroxide Lye.



Saponification Value

Amount of lye per ounce of oil

Example Amount Your Recipe Calls for:

Amount of Lye

(Multiply the saponification value by the ounces called for in your recipe)

Almond Oil


2 oz.

.272 oz. of lye

Avocado Oil


2 oz.

.266 oz. of lye

Beef Tallow


2 oz.

.28 oz. of lye

Bees Wax


2 oz.

.138 oz. of lye

Canola Oil

0.124 oz.

2 oz.

.248 oz. of lye

Castor Oil


2 oz.

.256 oz. of lye

Cocoa Butter


2 oz.

.274 oz. of lye

Coconut Oil


2 oz.

.38 oz. of lye

Grapeseed Oil


2 oz.

.252 oz. of lye

Hemp Seed Oil


2 oz.

.272 oz. of lye

Jojoba Oil


2 oz.

.138 oz. of lye



2 oz.

.276 oz. of lye

Olive Oil

0.134 oz.

2 oz.

.268 oz. of lye

Palm Oil


2 oz.

.282 oz. of lye

Shea Butter


2 oz.

.256 oz. of lye



2 oz.

.27 oz. of lye


Calculating your lye in your own recipe: Of course you will multiply the saponification value by the number of ounces for each oil. Then add up the separate calulations. This is your total amount of lye. Next, double the number and that will be how much water you use to disolve your lye.

Lye discounting and superfatting:

Once you have your calculations, you can choose to add extra oil to your soap batter. This is called “super fatting”. Each lye molecule bonds to an oil molecule creating the process called saponification. If we add a little extra oil, this means that there are more oil molecules than lye molecules and the extra oil has nothing with which to bond. When this happens, the oil will remain floating in the bar and give you a soft moisturizing bar. Typically, you will want your most nourishing oils like jojoba or vitamin E to float freely in your bar. A lye discount is the same thing, only instead of adding extra oils you subtract a little bit of the lye. Again, some oils will float freely and give you a moisturizing bar.

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