Cold process soap is a traditional method of soapmaking where natural oils and butters are blended with a lye solution to create real soap through a chemical process called saponification. Unlike many commercial cleansing bars, cold process soap is usually made in small batches and can retain naturally occurring glycerin, which helps the skin feel soft and moisturised.
What Does “Cold Process” Mean?
“Cold process” refers to the way the soap is made.
In this method, oils such as olive oil, coconut oil, castor oil, and shea butter are gently combined with a lye and water. The mixture is blended until it thickens, poured into moulds, and then left to harden.
After the bars are cut, they are cured for several weeks. During this time, excess water evaporates, the bar becomes harder, and the soap becomes milder and longer-lasting.
The process is called “cold” because no external heat is required after the oils and lye are mixed, unlike hot process soapmaking.
How Cold Process Soap Is Made
The cold process method follows several careful steps:
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Choosing the oils and butters
Soapmakers select oils and butters depending on the qualities they want in the final bar. For example, olive oil can create a gentle, conditioning bar, coconut oil helps create cleansing power and lather, and shea butter adds creaminess. -
Mixing lye with water
Lye, also known as sodium hydroxide, is mixed with water to create a lye solution. This step must be done carefully because lye is highly caustic before it reacts with the oils. -
Combining the oils and lye solution
Once the oils and lye solution are at the right temperature, they are blended. -
Saponification begins
The lye reacts with the oils and turns them into soap. This chemical reaction is called saponification. -
Adding natural extras
Ingredients such as essential oils, natural clays, activated charcoal, botanicals, or plant powders can be added for scent, colour, texture, and additional skin-loving benefits. -
Pouring into moulds
The soap mixture is poured into moulds and left to firm up. -
Cutting and curing
Once firm, the soap is cut into bars and cured for several weeks before use.
What Is Saponification?
Saponification is the chemical reaction that turns oils and lye into soap.
Although lye is used to make cold process soap, properly made and cured soap does not contain active lye in the final bar. The lye reacts with the oils during saponification, creating soap and glycerin.
In simple terms:
oils + lye = soap + glycerin
This is what makes cold process soap “real soap,” rather than a synthetic detergent bar.
Why Cold Process Soap Needs to Cure
Curing is one of the most important parts of cold process soapmaking.
During the curing period, the soap bars are left in a well-ventilated space for several weeks. This allows water to evaporate, which creates a harder and longer-lasting bar.
Curing also gives the soap time to become milder and more balanced. A well-cured bar generally lasts longer in the shower and produces a better lather.
Benefits of Cold Process Soap
Cold process soap is popular because it offers a more traditional, ingredient-focused approach to cleansing.
1. It Retains Natural Glycerin
Glycerin is naturally created during saponification. It is a humectant, meaning it helps attract moisture to the skin.
Many commercial soaps remove glycerin during manufacturing, but handmade cold process soap typically keeps it in the bar.
2. It Can Be Gentler on Skin
Cold process soap is often made with nourishing oils and butters rather than harsh synthetic detergents. This can make it a good option for people who prefer a simpler, more natural cleansing product.
3. It Allows Ingredient Transparency
With handmade cold process soap, you can usually see exactly what is inside the bar. Ingredients often include plant oils, butters, clays, essential oils, and botanicals.
4. It Avoids Unnecessary Additives
Many cold process soap bars are made without synthetic fragrances, sulphates, parabens, or artificial colours. This makes them appealing to people looking for a cleaner and more minimal bathroom routine.
5. It Supports Small-Batch Craftsmanship
Cold process soap is often handmade in small batches, allowing each recipe to be carefully formulated and cured with attention to detail.
6. It Can Be More Eco-Friendly
Soap bars usually require less packaging than liquid body wash or bottled hand soap. When paired with plastic-free or recyclable packaging, they can help reduce bathroom waste.
Swapping shop-bought soaps for natural cold process soap bars offers a range of benefits for your skin, health, and the environment. Commercial soaps often contain harsh detergents, synthetic fragrances, and preservatives that can strip your skin of its natural oils, leading to dryness, irritation, or sensitivities. In contrast, natural cold process soaps are made with nourishing oils, butters, and pure botanicals that gently cleanse while preserving your skin’s moisture and supporting a healthy barrier.
Cold process soaps retain natural glycerin, a powerful humectant that helps keep your skin soft and hydrated. They’re also free from unnecessary chemicals like parabens, sulfates, and artificial fragrances, making them a safer and more eco-friendly choice. By choosing handmade, natural soap bars, you’re treating your skin to gentle, effective care and supporting sustainable, small-batch craftsmanship. It’s a simple swap that can make a big difference for your well-being and the planet.
Cold process soaps don’t require added preservatives because their naturally high pH—typically around 9.5—creates an environment where bacteria and mold cannot thrive. This means your soap stays fresh and safe to use without the need for synthetic preservatives, making it a gentle and natural choice for your skin.
Cold Process Soap vs Commercial Soap
Many products sold as “soap” in supermarkets are actually synthetic detergent bars. These are often made with foaming agents, synthetic fragrances, preservatives, and other additives.
Cold process soap, by contrast, is created through saponification using oils and lye.
Key Differences
Is Lye Safe in Cold Process Soap?
This is one of the most common questions beginners ask.
Lye is essential for making real soap. Without lye, there is no saponification, and without saponification, there is no true soap.
However, in a properly formulated and cured cold process soap bar, the lye has reacted with the oils and is no longer present as active lye. The finished bar is safe to use when made correctly.
Common Ingredients in Cold Process Soap
Cold process soap can be made with a wide range of natural ingredients.
Olive Oil
Olive oil helps create a gentle, conditioning bar and is commonly used in traditional soap recipes.
Coconut Oil
Coconut oil contributes to cleansing power and helps create bubbly lather.
Shea Butter
Shea butter adds creaminess and a luxurious feel to the soap.
Castor Oil
Castor oil helps boost lather and creates a richer washing experience.
Jojoba Oil
Jojoba oil is valued for its skin-conditioning qualities and lightweight feel.
Natural Clays
Clays can add colour, texture, and a silky feel. Some clays are also used to help draw out excess oil and impurities.
Essential Oils
Essential oils provide natural fragrance and can add a refreshing, calming, or uplifting scent experience.
Plant Powders
Botanical powders such as turmeric, spirulina, nettle, or charcoal can be used for natural colour and added texture.
Who Is Cold Process Soap Good For?
Cold process soap may be a good choice for people who:
- Prefer natural ingredients
- Want to avoid synthetic fragrances
- Are looking for plastic-free bathroom swaps
- Like handmade skincare products
- Want a more traditional soap bar
- Prefer small-batch products
- Have dry or sensitive-feeling skin and want a gentler cleansing option
If you have very sensitive skin, allergies, eczema, or a diagnosed skin condition, it is always best to patch test first and check the ingredient list carefully.
How to Use Cold Process Soap
Using cold process soap is simple:
- Wet your hands, body, or face.
- Rub the soap bar between your hands or onto a washcloth.
- Create a creamy lather.
- Massage gently onto the skin.
- Rinse well.
- Place the bar on a draining soap dish so it can dry between uses.
Keeping the bar dry between uses helps it last much longer.
How Long Does Cold Process Soap Last?
A well-cured cold process soap bar can last several weeks, depending on:
- How often is it used
- How many people use it
- Whether it is kept dry between uses
- The recipe and hardness of the bar
- The size of the bar
To extend the life of your soap, store it on a soap dish with drainage and avoid leaving it sitting in water.
Is Cold Process Soap Better for the Environment?
Cold process soap can be a more eco-conscious option than bottled body wash or liquid hand soap.
Reasons include:
- Less plastic packaging
- Concentrated solid format
- Longer-lasting bars
- Often made in small batches
- Potentially lower shipping weight compared with liquid products
- Biodegradable ingredients, depending on the formulation
Final Thoughts
Cold process soap is one of the most traditional and thoughtful ways to make real soap. It combines simple chemistry with carefully chosen natural ingredients to create a bar that cleanses effectively while offering a more mindful alternative to many mass-produced products.
If you are looking for a gentle, plastic-free, and ingredient-conscious swap for your bathroom, handmade cold process soap is a great place to start.
Check our natural soap collection.