Cold Process Soap Making: How to Make Handmade Soap from Scratch

Two bars of dark handmade soap, make from scratch.

Learn about cold process soap making with this step-by-step guide to making soap from scratch. Discover the magic of combining natural ingredients with science to create gentle, homemade soap using the cold process of soap making.

Cold Process Soap Making: How to Make Soap from Scratch

Have you looked with longing at those beautiful bars of handmade soap on Pinterest or at craft shows? They range from pastel to deep colors, some with gorgeous veins of color swirled through them, and absolutely delicious fragrances.

Or are the loaves of uncut soap topped with rose petals or herbs and sometimes even glitter more your style?

I think they're all beautiful, but honestly, it wasn't just the artistry of those bars that intrigued me, it was the health aspect.

The thing is, commercial "soap" manufacturers use ingredients that aren't that healthy for us, such as parabens, triclosan, and sodium lauryl sulfate.

Not to mention the fact that commercial soap usually isn't really soap at all. Yes, seriously.

According to the Oxford dictionary, soap is "a substance used with water for washing and cleaning, made of a compound of natural oils or fats with sodium hydroxide or another strong alkali." [Source]

Look at the labels in the soap aisle the next time you're at the store. You'll find "beauty bars," "bath bars" and "deodorant bars."

Handmade soap is real soap, made from scratch.

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Homemade soap is customizable

When you make your own soap, you can use natural, healthy fats and oils, without the synthetic surfactants and chemicals that are in store-bought bars. 

And if you don't want to use a particular fat or oil, you can substitute another instead. (But you must calculate the correct amount of lye to use if you make substitutions. Don't worry, it's easy with an online lye calculator. More about that later.)

Soap projects can vary from simple 3-ingredient "recipes" to others containing seven or more oils ranging from common to exotic. Emu oil, anyone?

The easiest way to begin making your own soap is to use a simple recipe, so I'm going to share one that I started with so many years ago. 

This is a good "grocery-store soap," meaning you can probably find the ingredients in your local grocery store. 

But I'll include some links below in case you can't find them at your local grocery store, or if you want to source organic oils instead of what's in your local store.

Look in the health and beauty aisle for the castor oil, and on the cooking oil shelf for the others. (UPDATE: my local stores no longer carry castor oil; I had to order it online.)

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The basic cold process soap recipe in this article uses water as the liquid component, but soap can also be made from goat milk, tea, coffee and other alternatives too. 

I have a whole series of soap posts that go into more detail about each step in this article you're reading. If you need more information about any of these steps, be sure to read those posts as well. You'll find them all here.

Cold Process vs Hot Process soap

There are two methods of making soap: cold process and hot process (which is sometimes referred to as "crockpot soap"). 

They both start out the same way, with the same steps. When the soap batter has reached "trace," you can either pour it into the molds (cold process), or you can cook it to speed up the saponification process and reduce the curing time (hot process).

I prefer cold process, but many people, especially those who are new to soapmaking, prefer hot process.

What is cold process soap?

Once cold process soap is poured in the mold, it heats up in a chemical reaction called "saponification." I think it's kind of ironic that it's called cold process when it heats up and then cools down over a period of 24 hours or so.

But compared to the hot process, in which the soap is cooked for an additonal period of time, I suppose cold process soap isn't as hot.

Yes, cold process soap requires up to six weeks of cure time, but the end result is, in my opinion, nicer looking and I just like it better. I like the texture of cold process soap much better, too.

This post will teach you how to make cold process soap. I've written a post on how to make hot process soap if you'd like to try that method instead, or just want to compare the two before you decide.

The dangers of lye, and how to use lye safely

These are the safety procedures I use.
Please note that I am not responsible for accidents;
this post is for educational and entertainment purposes.

"Ugh, lye," you say. "Isn't that dangerous?"

It can be, yes. If you are careless and reckless, it can be quite dangerous. Lye (sodium hydroxide) is caustic, and can burn your skin and cause you permanent harm.

But if you treat lye with the respect it deserves and requires, you'll do just fine. Just follow the rules and be cautious.

Can you make soap without lye? No. 

You can, however, buy melt-and-pour soap bases that have already incorporated the lye for you. That's what we used when my granddaughter wanted to make soap.

So, even if you use a melt-and-pour soap base and you don't have to handle the lye yourself, your soap does contain lye.

Don't let lye scare you. The first time you make soap is the scariest, but after that it's much easier. 

After the first batch you know you'll survive the process. But like I said, you do have to treat it with respect, no matter how many times you've made soap in the past.

Lye is a caustic chemical that will burn your skin, and it would cause major damage if you splash it in your eyes or drink lye water. 

So we need to protect our skin from the lye, and ensure that we don't leave lye water where another person, child or pet can spill it or drink it.

Needless to say, you'll want to keep children and pets out of your soapmaking area while you're working. 

You might want to send your kids to the neighbors' house, or to their grandparents' home for the day. 

Put your dogs outside. Shut the cats in another room while you're working.

Safety precautions for soap making

Soap making safety equipment: gloves and goggles
My "mad scientist" protective gear. Always wear PPE when you are making soap with lye.

To protect yourself, you'll need some basic safety equipment.

Wear gloves such as you'd wear to wash dishes. These gloves are long and help to protect your wrists and forearms as well. Worn with a long-sleeved shirt, they'll protect your arms.

Wear safety glasses or goggles to protect your eyes. 

A mask will help to protect your face and also your lungs. Inhaling lye fumes can damage your lungs.

It does sound scary, doesn't it? But I want you to give lye the respect it demands. Wearing safety gear and working in a well-ventilated space will help keep you safe.

Do not touch the raw soap batter until after the saponification process has finished. Avoid spattering the batter while you're making your soap.

Always use the correct amount of lye, which will differ according to the oils you use to make your soap. 

Anytime you substitute a different oil for one in your recipe, you'll need to recalculate the amount of lye you'll need.

Don't worry, it's easy when you use a lye calculator. These handy online calculators will do the math for you. Simply input the oils and fats you plan to use and the calculator will tell you how much lye and how much liquid to use.

Soap making equipment

You'll need a few things to make soap. First, you'll need the protective gear we talked about above to protect you from the lye:

You'll also need:

  • a digital kitchen scale to weigh your oils, water and lye, such as this one that measures in both grams and ounces, and has a "tare" function which is so helpful.
  • two containers, one for the lye/water mixture and one for the oils. These should be heat-proof, and handles are handy. Don't use metal bowls or containers, some metals (aluminum, zinc and tin) react badly to lye. 
  • a plastic mixing spoon or two
  • a small dish or disposable cup to hold the lye while you weigh it
  • handheld stick blender or immersion blender such as this one. It will make your soapmaking life so much easier, trust me!
  • A mold to hold your soap batter while it turns into soap

My soapmaking equipment is only used to make soap; I don't use these items in my kitchen for any other use. For more information, read my post on soapmaking supplies and equipment.

Basic cold process soap recipe

Although I started out making soap with a 3-ingredient recipe, I soon reformulated it to include castor oil. Castor oil is what makes those little creamy bubbles in your soap lather that make it feel so luxurious.

Castor oil makes a big difference in your finished soap product.

Since then, I've added a few more ingredients to my own favorite recipe, but it's easiest to begin with a basic cold process soap recipe, so let's start with this one.

Note: all ingredients are measured by weight, not by volume.

Simple 4-oil soap recipe

Fats and Oils
14 oz Crisco* shortening
8 oz olive oil**

*Crisco oil is soybean oil, in a easy-to-find-and-purchase form. I recommend using the Crisco brand so you're using the same fat, as some cheaper brands might include other ingredients. 

(I've since replaced Crisco in my recipes with different ingredients, but this is an easy way to begin soapmaking, and it's super easy to find.)

**The color of the olive oil will affect the color of your finished soap. Choose a light-colored oil if you want a lighter-colored soap.

Liquid and Lye
12.16 distilled or filtered water (don't use tap water)

Optional: one ounce (by weight) of essential oil for fragrance. Peppermint, lavender or citrus essential oils are all excellent choices.

Using a batch sheet

I've developed my own checklist ("batch sheet") that I use for each batch of soap I make. It keeps me organized! All the oils are listed with their amounts, and I check them off as I measure them. 

I've made a printable soap batch sheet just like the one I use myself,
and I'll send to you for FREE.
Make as many copies as you need for your personal use.
Tell me where to send it in the form below.

Measuring the oils and fats

To measure the oils and fats you'll be using, set a small container or plastic cup on the scale and "zero it out" using the tare function, so it's only weighing the oil, not the container + oil.

A digital scale, container and a bottle of castor oil for soap making.

Pour in the oil until the container is holding the correct weight. Weigh carefully, you want to be as close to the recipe's directions as you can be. 

Making soap is chemistry; you need to be as exact as possible.

While you can continue to add the next oil to this container, I prefer to pour this first oil into the larger of my two heat-proof containers. I scrape as much of it out of the plastic cup as I can, and start over with the second oil.

Why? Because if I pour too much of the second oil into the container, how will I be able to spoon out enough of the right oil to reach the correct amount?

Continue until you have measured all the oils in the recipe. 

I've found it helpful to print out my recipes and check off each ingredient on my batch sheet as I weigh it so that I don't accidentally skip one. (Because I did that once! FAIL)

Weigh the amount of distilled or filtered water you'll need and add it to the second heat-proof container.

If you'll be adding essential oil to your soap, measure it into a plastic cup and set it aside until needed.  Measure it by weight, not by volume. 

Measuring the lye

Now it's time to measure the lye. Don your protective gloves and goggles, and a mask if you have one. Inhaling lye isn't good for your lungs. Work in a ventilated area.

Set a clean, dry container on your scale. A paper cup is handy, so that you can toss it in the garbage container when you're finished.

Zero out your scale using the tare function as before and weigh the amount of lye you need, as exactly as possible. Close the original container of lye. 

Set your weighed amount of lye where you're least likely to knock it over.

Melt the soap oils

I know, it seems like it has taken forever to get to this point, doesn't it? Maybe making soap takes too long?

Fear not - it takes as long to get set up to make soap as it does to actually make the soap. Maybe even longer.

Set up your work area by lining the table or counter with newspaper or towels. I prefer to work at the kitchen sink, so I protect the counter next to the sink.

A bowl of oils measured for soap making.

The first step is to melt the oils and fats. I personally melt the solid and semi-solid oils in the microwave in short bursts, then add them to the liquid oils in the heat-proof container.

You can warm them up using either the microwave or on the stovetop. Stir occasionally as you heat them up. 

Then set the oils aside while you mix the lye with the water.

Mix the lye water solution

If you don't still have them on, put on your protective gear for the next step: gloves and goggles or safety glasses.

With your measured water in a heat-proof container, sprinkle some of the lye slowly on the water and stir gently. 

Add a bit more and stir. Continue until you have mixed all the lye into the water. 

Don't add the liquid to the lye! You will end up with a dangerous volcano. ALWAYS add the lye to the liquid, and add it slowly.

Think of it as adding salt to a steak, or snow on a mountain, whichever paints the best picture in your mind that you will remember. Sprinkle the lye on the water.

This container with the lye water solution will heat up, so I like to use a container with a handle. It will also generate fumes, so working in a well-ventilated area and wearing a mask are a must.

Set both containers aside in a safe place where children and pets can't reach them, and wait until both containers are about the same temperature. 

How long will it take for the containers to reach the same temperature? It will depend on the temperature in your kitchen (or wherever you're working) among other factors.

When the melted oils and the lye water are approximately the same temperature (you don't need to use a thermometer, just feel the outside of the containers), you're ready to go!

Remember, whenever you are working with lye, you should banish pets and children from your working area. Don't answer the phone. Don't be distracted by Facebook.

Mixing the oils and the lye/water solution together

This is important: add the lye water to the oils, not the other way around. 

Just like when you added the lye to the liquid in the previous step. Remember that you're always adding the lye TO the other ingredients.

I set my mixing bowl of oils in the kitchen sink; it's a comfortable height for stirring for me. I pour the lye water into the mixing bowl of oils and stir with your big plastic spoon.

A green plastic bowl of handmade soap batter.

Mixing the soap batter

My handheld stick blender is one of the best tools I've ever bought. It's only used for soapmaking, never for food preparation.

Use the stick blender for a minute or two, to blend the oils and the lye water.  Then turn it off and stir with the spoon, or stire by hand with the mixer while it's turned off. 

Alternate using the mixer and stirring by hand to avoid burning out the mixer's motor. 

Be careful to hold the mixer upright so it doesn't splash soap batter.

The soap mixture starts out looking translucent, but as you stir it will begin to turn opaque. Eventually the soap batter will become thicker. 

When you can see the "track" of the mixer or your spoon as you drag it through the soap batter, you are near "trace". Trace is the magic, miraculous stage you're working towards!

Light trace is when you can see the track of the spoon in the batter; heavy trace looks like thick pudding.

A bowl of soap batter that has reached trace.
This batch of soap batter has reached "trace." You can see the track of the spoon as it was dragged through the batter.

I like to pour my batter into the mold when it's at a medium trace.

If you wish to add essential oil to your soap, this is the time to do it. Pour it in and use your stick blender to mix it in.

Pouring the soap batter into the mold

Now that your soap batter has reached trace, it's time to pour your soap into the mold!

This recipe should fit into a 40-oz mold such as this one. I bought mine from Amazon but they are also available from online soap supply companies. 

I have another, slightly different one from Michael's that holds a bit less than 40 ounces.

Raw soap batter poured into a soap making mold.
See that bubble in the bottom left of the mold? I used my spatula to fill that back in.

Pour the batter slowly into the mold to prevent bubbles, which will leave holes in your finished soap. 

You can carefully tap the mold on the counter to dislodge any additional bubbles that might have formed, but not hard enough that soap will splatter out of the mold. 

Now you'll set the mold aside and let it turn into soap - keep reading for the directions.

Cleaning your soap equipment

"But Kathi, if the soap batter is caustic, how can I clean it all up when I'm done?"

That's a good question. Here's what I do:

I don't have children at home, but I do have pets. In particular I have a cat that jumps on the kitchen counters even though he knows he's not supposed to. (I'm looking at you, Thor.) 

I'm careful to protect the cats, dogs and people!

Washing up the bowls and equipment after making soap.

After I pour my soap batter into the mold and while still wearing my protective gloves and glasses, my clean-up routine consists of putting all my tools (mixing spoon, spatula, stick blender, etc.) inside the larger bowl, then put it all inside a garbage bag and tie a knot in the bag.

Then I put the whole thing on a high shelf in the mudroom; the door to this room is always closed because the mudroom isn't heated or air-conditioned. 

You might have a shelf in the garage that would work.

I leave the bag there, untouched, until after I unmold the soap. Why? Because by then the soap batter has saponified and it's soap. It's no longer caustic.

Then I fill the sink with hot water and let it all soak for a bit so the hardened soap can soften, and I wash it all. 

No need to wear gloves, because I'm simply washing my equipment with the soap I just made.

The newspaper that lined the kitchen counter is rolled up and disposed of, or the towel folded up and washed immediately.

Cutting and curing your soap

After pouring your soap into the mold, set it in an undisturbed place for about 24 hours, where children and pets can't get into it. 

During this time the soap will saponify, which is the chemical process of turning into soap.

The soap batter will heat up and the saponification process will proceed. You can watch the opaque soap go through a "gel stage" and then once again turn opaque - although it's rather like watching paint dry.

Two bars of handmade soap tied prettily together with brown cord.

Removing the soap from the mold

After 24 hours, if the soap seems solid enough, you can remove it from the mold. If it's still a bit too soft, leave it for another 12-24 hours.

I let this uncut loaf set for up to another day before cutting it into bars. Use your judgement, it might need longer before you can cut it. 

And yes, it's ok to touch the soap without gloves at this point.

I use a miter box to cut my soap into bars. It was hubby's ingenuous idea!

Set the bars on edge on white paper towels and let them cure for four to six weeks, turning occasionally.

I know, six weeks is an eternity! But your soap will be harder and longer-lasting the longer it cures.

Your soap is ready to use - or package a bar or two in a pretty basket to gift to some of your favorite people!

This post contains affiliate links; if you click on a link and make a purchase I might make a small commission but it doesn't affect the price you pay. Read my disclosure here.


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