The Best Oils for Soap Making

Using different oils and fats will give your soaps different properties. Learn how to harden, add lather, and improve soaps by varying the oils in the recipe.

Choosing oils for soap making isn’t like choosing oils for a homemade lotion or body butter.

When making our own cosmetics, we get so accustomed to using certain oils, that we want to use those oils in everything we make. I often get questions from people about switching out oils in a soap recipe because they like a certain oil better than the oil in that recipe.

Just because you love your homemade lotion made with 100% hemp oil, though, doesn’t mean that a soap made with 100% hemp oil is going to be great!

Saponification is a chemical reaction

When we make soap, we are completely altering the ingredients in a chemical reaction called saponification.

One of the reasons that some people are afraid to make their own soap is because they are afraid of using lye. Or, they are afraid that their soap has “lye in it.”

Lye is an essential ingredient in soap making. It reacts with the fats in your recipe to make a completely different material: soap!

Just as your finished soap will no longer have “lye in it,” the oils you used will no longer have the same properties.

Yes, it’s possible to “superfat” a soap so that it arguably contains unreacted oils in it, but even in those cases, you probably can’t really tell that much of a difference what the “extra” oil is.

Soap oil properties

So, the oils in your soap will act differently than they did before the chemical process took place.

When you make a homemade lotion, you aren’t really altering the fats in the recipe. Yes, you do emulsify them with water, but that’s basically just suspending small particles of the oil within the water. It allows us to apply the oils and water together to our skin so that we can hydrate and moisturize it.

On the other hand, when you make soap, the different fats will act in different ways. Knowing the tendencies of the different oils and other fats in soap making will help us formulate an ideal soap bar for whatever our chosen purpose.

Solid fats tend to make hard bars

If you’re looking to make a hard bar of soap, choose a high percentage of solid fats. Solid fats are the ones that are generally solid at room temperature like coconut oil, palm kernel oil, or animal fats like lard and tallow.

Most liquid oils won’t make a solid bar of soap and need to be combined with a solid fat to make a decent, usable bar.

That said, olive oil is an exception. It takes a bit longer to harden up than the solid fats, but can harden into a decent, hard bar soap.

Oils in soap making

So, let’s explore how some of the more common oils behave in soap making.

Olive oil

Olive oils is one of my favorite oils for making soap. It’s inexpensive and provides a “conditioning” feel to the soap. That makes it a great oil for face and body soaps.

On the other hand, soaps made with only olive oil aren’t as cleansing and don’t provide much of a lather.

Soaps made with 100% olive oil are called pure Castile soaps. Some people, especially those with sensitive skin, love pure Castile soap because it’s gentle and not as drying as some other soaps. On the other hand, other people hate it. They think it feels “slimy” or are upset that it doesn’t provide much lather.

When it comes to liquid soaps, I haven’t found there to be the same issues. My pure liquid Castile soap actually does provide lather, and my liquid coconut oil soap isn’t as drying or harsh as I would have expected.

Coconut oil

Coconut oil is another one of my favorite oils for soapmaking. It provides a lot of lather and soaps made with coconut oil do a great job cleaning. I made my easy laundry soap with 100% coconut oil.

On the downside, soaps made with only coconut oil are said to be drying. That’s why it isn’t used alone in most soap recipes. You can , however, counteract that by superfatting by a large percentage, even to around 20%. (Superfatting is when you add more oil/fat than what is needed to make soap so that some unreacted oil remains in your soap.)

As I stated earlier, when it comes to liquid soaps, I haven’t noticed the same differences that I’ve noticed with bar soaps. A bar soap made with 100% olive oil is completely different from a bar soap made with 100% coconut oil.

On the other hand, I have a hard time distinguishing the various liquid soaps I have at home. I’ve used my homemade liquid coconut oil soap in the shower for years now and don’t find it especially drying.

Castor oil

Castor oil can make a soap more easily dissolved in water. It also helps boost and extend lather time. That’s why it’s a great addition to shave soaps.

If used at too high a percentage (over 10%), though, it can make a bar of soap feel sticky. For most soaps, using up to around 5% is a good amount to use.

Castor oil can also work as an extra solvent when added to translucent soaps like glycerin soaps.

Animal fats (Lard and tallow)

Animal fats make hard bars of soap with good cleansing abilities. You can make a good laundry soap with 100% lard or tallow. Normally, though, I suggest adding them up to 50% of a recipe to give a good stable lather.

In my first glycerin soap recipe, I used tallow to help make a hard bar of soap. When making glycerin soaps, solvents are used to remove part of the crystalline structure of the soap. That’s what gives the soaps a translucent appearance. If you don’t start with a hard bar of soap, the solvents would make a soft soap even softer!

For my peppermint holiday soap, I chose to add both coconut oil and lard to make a hard, white bar of soap. Because soaps made with hard oils also harden up quickly, I was able to make the peppermint candy design in a short time.

Laurel Berry Oil

Laurel berry oil is the oil that’s used together with olive oil in the traditional Aleppo soaps made in Aleppo, Syria. It may add a bit of lather to an otherwise low-lather Castile soap.

It’s usually added at around 20-40% of an otherwise pure Castile soap.

Liquid oils (Jojoba, avocado, sunflower oils, etc.)

Many liquid oils can be used up to 10-15% in soap recipes for medium lather and mild cleansing. When used in higher concentrations, the bar of soap can become too soft or the soap or can even go rancid prematurely.

Jojoba oil is really a liquid wax, but it mostly behaves like the liquid oils in soap making. It is more stable than them against rancidity.

When using liquid oils, it generally takes longer to reach trace during soap making. It also may take longer to harden up enough to unmold.

Butters (Shea, Cocoa, Mango)

Butters like shea butter, cocoa butter, and mango butter tend to help make hard bars of soap with stable lather. Using them up to around 20% of a soap recipe is a good amount to shoot for, but they can be used in higher amounts.

Waxes

A tiny amount of wax, such as beeswax, can also help harden the soap. Too much, though, can completely kill the lather and make the soap sticky. Around 1-2% of the oil portion of the recipe is a good maximum amount to add.

Combining oils

To get the benefits of several different oils in a way that complement each other, most soaps use a combination of a variety of oils.

Liquid oils are used for their moisturizing and/or conditioning properties. They tend to make mild soaps, but if used alone, they can make bars of soap that are too soft. Olive oil is the exception and can make a hard bar of soap, albeit one that doesn’t lather much.

Some people love pure Castile soaps for their mildness. Other people hate them and say they are too slimy and don’t lather.

To help harden the soaps, increase their lather, and improve their cleansing ability, hard oils are added to the soaps. If you are using olive oil as the main liquid oil, only a small amount of hard oil is needed to improve the qualities of the soap. Otherwise, it’s good to shoot for at least 50% of the oils to be solid oils.

My easy beginner soap recipe is an example of what some call a “Bastile” soap. Bastile soaps are modified Castile soap recipes. They are mostly olive oil-based but have the addition of another oil/other oils. In that recipe, I added some coconut oil to improve the lather and cleansing ability.

That soap has become very popular. People love the simplicity of making a soap with oils that are very easy to find. If you’ve never made soap before, it’s a great place to begin your soap making journey!

Because that post was so popular, I based a couple of other recipes on it. They each were based on the same oil combination.

In my post with a recipe for pumpkin spice soap, you learn how to add goat milk to your soap so that it won’t be scorched. It also teaches you how to use a basic swirling technique to add a fun look to your soaps.

Another holiday soap based on that recipe is my gingerbread soap. It incorporates molasses for color and a mild boost in lather.

Helping find the best combination

Once you know the basic tendencies of the oils in soap making, you can start experimenting with formulating your own soaps.

To do so, a lye calculator is a very helpful tool. It allows you to calculate how much lye to use in your recipe.

Soapcalc has a great lye calculator that can actually help you predict what your soap will be like. It will give you certain numbers for qualities like “hardness”, “Cleansing”, “Conditioning”, “bubbly”. The numbers may be confusing at first. If you click on the “view or print recipe” button, though, a new tab will be opened with all sorts of information about your recipe.

Next to the numbers for your soap’s qualities, you’ll also see a good range for each property. It gives you a guideline to shoot for. At first, you may want to stick to trying to get within the ranges for all of the properties. With time and experimentation, though, you may find that you like some soaps outside of those ranges. It’s all a matter of each person’s preferences, of course.

For more information about how to use a lye calculator, check out the following post…