The Best Oils for Soap Making (and What Each One Does)

Every bar of soap starts with a fat or oil reacting with lye. But not all oils behave the same way. Some make your bar hard and long-lasting. Some load it with bubbles. Some keep skin from feeling stripped. Getting the balance right is what separates a bar that lathers beautifully from one that goes soft in the dish or feels tight after rinsing.

This guide walks through the oils beginners reach for most often, explains what each one actually does, and gives you realistic usage percentages to build your first recipe around.

What Oils Actually Contribute to Soap

Before jumping to specific oils, it helps to understand the properties you're trying to balance. Soap formulators talk about a handful of qualities:

Hardness

A hard bar lasts longer in the shower and unmolds cleanly. Oils high in saturated fatty acids (lauric, myristic, palmitic, stearic) produce harder bars. Coconut oil, palm oil, and cocoa butter are the main contributors here.

Cleansing

This refers to how well the soap removes oils and dirt from skin. High-lauric oils (primarily coconut) are powerful cleansers. That's an asset, but too much becomes aggressive, stripping the skin's natural moisture barrier.

Bubbly vs. Creamy Lather

These are two different kinds of foam. Coconut oil and castor oil produce big, fluffy bubbles. Olive oil and shea butter produce a dense, creamy lather. Most people want a mix of both, so blending oils matters.

Conditioning

Conditioning describes how skin feels after rinsing. Oils high in oleic acid (olive, avocado, sweet almond) leave skin feeling soft rather than squeaky. They're also gentler for sensitive or dry skin types.

Stability

An unstable soap goes rancid quickly, developing a yellow-orange oily layer called "dreaded orange spot" (DOS). Oils with short shelf lives (grapeseed, hemp seed, unrefined walnut) can speed up rancidity when used in large amounts. Balancing with more stable oils extends shelf life.

The Core Beginner Oils

Most first-time soap makers work with five or six oils. These cover every important property and are easy to source.

Olive Oil

Olive oil is the default starting point for a reason. It's high in oleic acid, which makes a gentle, conditioning bar with a creamy, stable lather. It's slow to trace (good for beginners who need time to work), and it's widely available.

The trade-off is hardness. A soap made from 100% olive oil (called Castile soap) takes weeks to cure before it hardens properly. In a beginner blend, olive typically makes up 40–70% of the oil weight, providing the conditioning backbone while other oils handle hardness and bubbles.

Coconut Oil

Coconut oil does two things extremely well: it makes hard bars, and it produces generous, bubbly lather. It also rinses cleanly even in hard water, which is a real-world advantage.

The limitation is that it can be drying at high concentrations. Keeping coconut oil at or below 30% of your oil weight is the standard advice for a bar intended for regular skin. Some formulators go as low as 20% for very sensitive skin or facial bars. If you see a recipe with 40%+ coconut, it's usually a clarifying or dish soap, not a skin bar.

Palm Oil (or a Palm-Free Substitute)

Palm oil contributes hardness and a stable, creamy lather, and it's one of the main reasons commercial soap bars hold their shape so well. In a recipe, it typically sits at 20–35%.

Palm oil carries significant environmental concerns around deforestation, so many soap makers now substitute it entirely. The most common palm-free alternatives:

• Lard or tallow: Renders well, produces a hard bar with excellent lather. Lather quality is often considered superior to palm. Around 20–35%.
• Cocoa butter: Adds hardness and a very slight natural scent. Best used at 5–15% (higher amounts can make the bar brittle and reduce lather).
• Sodium lactate: Not an oil, but used as an additive to help unmold faster when going palm-free.

A palm-free bar blending olive, coconut, and shea with a small amount of castor is a clean, effective starting point.

Shea Butter

Shea butter is rich in stearic and oleic acids, making it a double-duty ingredient: it adds conditioning properties and contributes to bar hardness. At 5–15%, it adds a silky feel to lather and improves skin feel noticeably. Above 15% it can make tracing faster and the finished bar slightly waxy.

Refined shea butter has a neutral scent and is easier to work with than unrefined for fragrance-forward recipes. Both work equally well for skin properties.

Castor Oil

Castor oil is used in small amounts for one specific reason: it boosts lather. It's high in ricinoleic acid, which is unusual among oils and has a strong affinity for bubbles. Around 5% castor oil in a recipe makes a noticeable difference to lather volume and stability.

Keep it low. Above 8–10%, castor oil can make your bar soft and sticky. It's a supporting ingredient, not a base oil.

A Practical Oil Comparison Table

Oil	What It Contributes	Typical % in Recipe
Olive oil	Conditioning, creamy lather, gentle cleanse	40–70%
Coconut oil	Hardness, bubbly lather, strong cleansing	20–30%
Palm oil	Hardness, stable lather (or use a substitute)	20–35%
Shea butter	Hardness, silky conditioning	5–15%
Cocoa butter	Hardness, creaminess	5–15%
Castor oil	Lather boost	3–8%
Lard / tallow	Hardness, creamy lather (palm substitute)	20–35%
Avocado oil	Extra conditioning, soft skin feel	5–20%
Sweet almond oil	Conditioning, mild and skin-friendly	5–15%

How to Build a Balanced Beginner Recipe

A well-balanced beginner recipe doesn't require a dozen oils. Three or four, chosen intentionally, produces a better result than eight oils in arbitrary amounts.

Start with your base

Olive oil as the majority oil (50–60%) gives you a gentle, conditioning foundation. It handles the skin-feel side of the equation.

Add a hard, cleansing oil

Coconut oil at 25–30% handles bubbles, hardness, and cleansing power. If you're making a gentler bar, pull this back to 20%.

Add a hardening butter (optional but helpful)

Shea butter at 10% improves both hardness and the skin feel of the finished bar. Cocoa butter works too, but keep it at 5–10% or the bar can feel draggy.

Finish with castor

Five percent castor oil rounds out the lather. It's a small amount, but you'll notice the difference.

A starting recipe might look like: olive 55%, coconut 28%, shea 12%, castor 5%. That's a balanced, beginner-friendly bar with good lather, reasonable hardness, and conditioning properties.

Every recipe needs a lye calculator

This is non-negotiable. Each oil has a different saponification (SAP) value, meaning the precise amount of lye required to fully convert it to soap varies. You cannot use the same lye amount for a coconut-heavy recipe and an olive-heavy one. Even small miscalculations produce soap that is either lye-heavy (caustic, unsafe) or un-saponified (greasy, soft).

Run every recipe through a free lye calculator (SoapCalc and Brambleberry both offer reliable ones) before you mix anything. Enter each oil by weight and percentage, set your superfat percentage, and let the calculator determine your lye and water amounts. Do not skip this step.

For more detail on the water side of the equation, see how much water to use in cold process soap.

Oil Substitutions and Flexibility

Recipes are more flexible than beginners often think. Swapping olive for avocado oil works nearly 1:1. Replacing palm with lard produces a comparable bar. Dropping shea and adding more olive changes the texture slightly but still yields good soap.

What matters is keeping the type of fatty acids roughly balanced. If you swap out all your saturated fats for liquid oils, your bar will be soft. If you swap out all your conditioning oleic-rich oils for hard saturated ones, your bar may be harsh on skin.

Once you've made a simple beginner cold process soap recipe and gotten comfortable with the process, experimenting with oil ratios is genuinely enjoyable. Keep notes on what each batch feels like in the mold, how quickly it hardens, and what the finished bar is like after cure. That feedback loop teaches you more than any single recipe can.

Frequently Asked Questions

Can I use just one oil for a beginner batch?

Technically yes. A 100% coconut oil soap is popular as a laundry or dish bar. A 100% olive oil Castile soap is very gentle and good for sensitive skin, but it takes 4–6 weeks to cure properly and the lather can feel thin until it's fully cured. For skin soap, a blend of two or three oils gives better all-around results from the start.

Is there a rule for how many oils to use?

No hard rule, but beginners do better with fewer oils (three to five) rather than more. Each new oil adds complexity to your lye calculation and shortens your troubleshooting options if something goes wrong. Build confidence with a simple recipe first.

Why does coconut oil dry out skin if it's so popular in soap?

Coconut oil is high in lauric acid, which is an excellent cleanser but also strips sebum (the skin's natural oil) aggressively at high concentrations. At 25–30% in a recipe, it's balanced by conditioning oils. At 50% or more, most people notice dryness. The recipe percentage matters more than the ingredient itself.

Do I need to buy special soap-making olive oil?

No. Regular food-grade olive oil works fine. Pomace olive oil (a refined grade made from the pressed olive pulp) actually behaves slightly differently at trace and some formulators prefer it, but for a first batch, any olive oil from the grocery store is adequate. Avoid olive oil blended with other oils (check the label), since the mixed composition affects your lye calculation.

What about oils like hemp seed, grapeseed, or rosehip?

These are popular in skincare for their skin-benefit profiles, but they're high in linoleic acid and have short shelf lives. In soap, they accelerate rancidity (DOS) over time, especially in bars you plan to cure and store for weeks. If you want to include them, keep the percentage low (5–10%) and use your bars within a few months of curing. For a beginner recipe, leave them out until you have the basics down.