How to Balance a Natural Soap Recipe

Creating a soap recipe is not simply about adding several oils at random. Each fat brings its own qualities. Some contribute to hardness, others to lather, mildness, or a creamier feel. The goal is therefore not to find the perfect recipe, but to build a formula in which the different oils complement one another.

In cold process soapmaking, the fatty acids found in oils and butters contribute specific properties. Balancing these fatty acids can help create hardness through saturated fatty acids such as lauric, myristic, palmitic, and stearic acids; lather, mainly provided by lauric and myristic acids and supported by stearic and ricinoleic acids; and a milder, more conditioning feel, associated with oleic and linoleic acids.

1. Start with the role of each oil

Before choosing the percentages of your oils, ask yourself what kind of soap you want to make. Then choose your ingredients according to the characteristics you are looking for.

Oils rich in lauric and myristic acids: Such as coconut oil, these contribute to abundant lather and cleansing power, but can make a soap more stripping when used in high amounts.

Fats rich in palmitic and stearic acids: Such as shea butter or cocoa butter, these contribute to hardness and help create a more stable, creamy lather.

Oils rich in oleic acid: Such as olive oil, these generally produce a mild soap with a creamier, less bubbly lather.

Oils rich in ricinoleic acid: Such as castor oil, these help support and stabilize lather, but are generally used in small amounts, around 3–10%.

Oils rich in polyunsaturated fatty acids (linoleic and linolenic acids): Such as sunflower or hemp seed oil, these can contribute an interesting skin feel, but should be used thoughtfully because they can make a soap more susceptible to oxidation.

A good recipe therefore starts with one simple question:

What is each oil supposed to contribute?

2. Build a foundation

For a first formula, it can be easier to work with three main groups:

one main oil + one or two structuring fats + one small functional oil.

For example, you could use a liquid oil as your main base, a harder oil or butter to provide structure, and a small amount of castor oil to support the lather.

This makes it easier to understand the role of each ingredient before working with more complex formulas.

3. Look for balance rather than maximum values

More lather does not necessarily mean a better soap.

More butter does not necessarily mean a milder soap.

And a recipe containing ten different oils is not necessarily more sophisticated than one containing three.

A balanced soap is instead one that brings together several qualities:

Hardness + cleansing + mildness + lather + stability.

Sometimes, improving one characteristic can affect another. For example, increasing the amount of coconut oil can give you more lather and cleansing power, but it can also make the soap feel less mild for some skin types.

This is where formulation becomes interesting. You are not trying to maximize every single property. You are trying to find harmony between them.

4. Look at percentages, not just grams

A recipe can look balanced when expressed in grams without actually being balanced.

That is why it is useful to work with percentages of total oils first.

For example:

• 30–70% main oil

• 15–25% structuring oil

• 5–20% butter

• 3–10% castor oil

Once your formula has been defined, you can calculate the number of grams needed for your desired total oil weight.

And most importantly, whenever you change an oil, even slightly, recalculate the amount of lye required. Each oil has its own saponification value.

The Main Oil Families

These categories are simply guidelines. The same oil can play several different roles in a formula.

5. Build a recipe step by step

A simple approach is to start with one main oil and build the formula around it.

1. Choose your base

Ask yourself what kind of feel you are looking for.

A mild and creamy soap?

A bubbly soap?

A very hard bar?

A soap intended for frequent use?

Your main oil will already give your formula a particular direction.

2. Add a structuring fat

Next, add a butter or another fat richer in saturated fatty acids to provide hardness and structure.

Think of it as giving the formula a backbone.

3. Add a complementary oil

A third oil can then bring in a specific characteristic: mildness, slip, lather, or a particular skin feel.

4. Add a small amount of castor oil

If you want to work on the lather, a small amount of castor oil can complement the formula.

You do not need much. In soapmaking, castor oil is generally used in relatively small amounts.

Example of a Formula Build

Let's imagine starting with this recipe:

• 50% olive oil → mild base

• 25% coconut oil → cleansing and lather

• 17% shea butter → structure and creaminess

• 8% castor oil → lather support

This is not a universal recipe. It is simply an example to show how different roles can complement one another.

You could then gradually change one element at a time:

• less coconut oil if you want to reduce cleansing power;

• more butter if you want more structure;

• less castor oil if you want a simpler formula;

• replace one oil with another to explore a different skin feel.

Every time you make a change, the lye calculation must be redone.

6. Check your recipe with a lye calculator

Once you have chosen your oil composition, use a soap calculator to determine the amount of NaOH required.

You can then adjust the superfat, lye concentration, water amount, and batch size.

However, a calculator does not replace understanding your recipe. It gives you the numbers required for saponification; you are the one deciding how the formula is structured.

You can also read my article about my three favorite soap calculators.

7. And then? Observe the soap

A recipe should not be judged only on paper.

After the cure, observe your soap:

Is it hard enough?

Do you like the lather?

Does it rinse easily?

Does the skin feel comfortable after use?

Does the soap behave well over time?

These observations are valuable. They allow you to gradually refine your formula rather than changing several variables at once.

The Small Principle to Remember

A balanced soap is not the one that contains the most oils or gets the highest numbers across every category.

It is the one where each ingredient has a reason for being there and the ingredients work well together.