One of the questions that I get asked most often is, “How do I make my soap harder?

How to Make Handcrafted Soap Harder

Here are a few ideas to get you started. It really takes experimenting to find what works best for your recipe.

how to make harder soap

Evaluate Your Oils

Take a look at your recipe. What is your percentage of hard oils and soft oils? For the most part, hard oils and butters make a hard bar of soap and liquid oils make a soft bar of soap. There are two exceptions.

Olive oil – Olive oil is initially soft upon unmolding but cures out rock hard. Have you heard of or used castile soap before?

Castor oil – Castor oil is another oil that starts off soft and sticky in soap but cures to be hard.

If your recipe is full of any other liquid oils such as rice bran, soybean, avocado, sunflower…etc., these will make a soft bar of soap.

My typical mix of oils is something like this:

Coconut oil – 34% (Hard)
Olive oil – 34% (Hard)
Avocado oil – 8% (Soft)
Rice bran oil – 14% (Soft)
Shea butter – 10% (Hard)

This makes an excellent bar of soap. For more info on oils in soapmaking, download my free Soapmaking Oil Chart!

Evaluate Your Superfat

What percentage of excess oil remains unsaponified in your soap? A higher amount produces a softer soap. If you are superfatting your soap at 8%, try 5% and see if that helps.

Olive Oil

Which olive oil do you use? From personal experience, I have found that Refined A or Regular olive oil is the best olive oil to use when making soap. I usually get Refined A from

I know lots of soapmakers use pomace olive oil (mainly for the price) but I stay away from it. Pomace has many unsaponifiables in it which make for a soft soap and is also usually tinted a funky green color that messes with my color additives. I do not like pomace olive oil…at all.

Don’t take my word for it, though. Do a side by side test with pomace and refined A and see which you prefer. (I bet refined A wins.) The refined A will come out lighter in color and harder (especially after the cure).

Stearic Acid or Beeswax

Both of these ingredients will harden your soap. Both of these ingredients can also be tricky to work with. You have to soap at hotter temperatures to make sure they don’t solidify in your mixing pot.

I personally don’t use them because I soap at cool temps. If you do want to experiment with them add 1/4-1 teaspoon (per pound of oils) of either beeswax or stearic acid to hard oils/butters and melt.

Sodium Lactate

Sodium lactate is used by soapmakers to make a harder bar of soap. I used to use it a lot…until I learned to better formulate recipes without it.

You can get info on how to use it at Bramble Berry’s website here. Start with 1/2 teaspoon per pound of oils (added to cool lye solution) and go up from there.

If you use too much, it can make your soap crumbly where it breaks easily.

Add a Pinch of Salt to Lye Solution

Salt adds initial hardness to cold process soap. Here is an article from David at about adding salt to soap.

I actually add it after I mix the lye so the hot lye solution easily melts the salt.

It is important to note that salt does kill lather in higher quantities. Have you ever made a salt bar? So if you want to experiment with adding salt in higher quantities, just know that you can lose some lather.

1/4-1/2 teaspoon per pound of oils seems to be the ideal range.

What do you do to make a harder bar of soap?

I’d love to know what you do! If you are a soapmaker and can offer advice for hardening soap, please do so in the comments!

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Happy Hard Soapmaking!

-Amanda Gail