What Is Cold Process Soap — And Why Does It Matter?

Walk into any supermarket and pick up a "soap" bar. Turn it over. Chances are the word "soap" doesn't appear once on the label. Instead you'll find "beauty bar", "cleansing bar", or "syndet bar" — because legally, most commercial products aren't soap at all.

Real soap has been made the same way for thousands of years: combine oils with an alkali, wait, and you get something that cleans gently and leaves your skin better than it found it. Cold process soap is that thing. Here's what it actually means — and why it makes a difference.

What is cold process soap?

Cold process (CP) soap is made by combining oils and butters with sodium hydroxide (lye) in a chemical reaction called saponification. The result is real soap — fatty acid salts that clean effectively without stripping your skin's natural moisture barrier.

The "cold" in cold process refers to the fact that no external heat is applied during mixing. The saponification reaction generates its own heat as it happens. After the soap is poured into the mould, it cures for 24-72 hours, during which the reaction completes fully and the bar hardens.
The bar then needs four to six weeks to cure. During that time, excess water evaporates and the bar hardens into the dense, long-lasting form you use in the shower.

What's left at the end is a bar made of exactly what you put in — and nothing else.

How it's made: oils + lye + water

Every cold process soap starts with oils and butters. These contain fatty acids — the building blocks that determine how a soap behaves: how hard it is, how creamy the lather is, how moisturising it feels.

When you add lye, specifically sodium hydroxide (dissolved in water) to those oils, the saponification reaction begins. Each fatty acid molecule bonds with a sodium ion from the lye, forming a soap molecule. The glycerin that was originally part of the oil is released as a by-product — and stays in the bar.

That last part matters. Commercial soap manufacturers remove the glycerin during production and sell it separately to the cosmetics industry, or they add it to the detergents as a synthetic ingredient to create something similar to a soap. In cold process soap, the glycerin stays where it belongs — in the bar.

source: jennifer soap

Why it's different from cheap commercial soap

Most bars you find in supermarkets are not soap in the traditional sense. They're made through a detergent process using synthetic surfactants — compounds derived from petroleum that clean by stripping everything from your skin, including the oils your skin actually needs.

Here's what typically goes into a commercial soap bar:

• Synthetic surfactants (sodium lauryl sulfate, sodium laureth sulfate) — strip oils aggressively
• Preservatives — required because the formulation contains water-based ingredients that would otherwise spoil
• Palm oil derivatives — used for cheap hardness, often from uncertified sources
• Glycerin removed or synthetic one added — extracted during manufacturing and sold separately or added a cheap synthetic version as a humectant.

Cold process soap contains none of these by necessity. The saponification process itself is the preservative — lye eliminates pathogens during the reaction and the high pH and no available water does not allow bacteria to take hold on a soap. 

What cold process soap does for your skin

Because cold process soap retains its glycerin and is made entirely from oils and butters which can be fully or partially saponified (e.g. 5-8% superfat is normal in cold process soaps - means 5-8% of those oils and butters remain in their original form in the soap), it interacts with your skin very differently to commercial bars.

It cleans without stripping. The soap molecules lift dirt and excess oil, but the glycerin and residual conditioning oils left behind mean your skin isn't left feeling tight or dry.

It maintains your skin's pH balance better. Commercial detergents can disrupt the skin's slightly acidic pH. Cold process soap, while moderately alkaline itself (pH 8-9), rinses clean and causes less disruption over time — particularly for sensitive skin. 

It works with your moisture barrier, not against it. The fatty acids in the oils used to make the soap (olive, coconut, shea) mirror the lipids in your skin, supporting rather than stripping the natural barrier.

The ingredients we use at the curated — and why

Every bar we make starts with the same core oils, chosen for what they each contribute to the finished soap.

Olive oil gives the soap a gentle, skin-conditioning character. It's high in oleic acid, which makes lather creamy rather than fluffy and leaves skin feeling soft.

Rapeseed oil is our local Swiss workhorse — sustainable, high in linoleic acid, and excellent at producing a stable, conditioning lather.

Coconut oil provides the hardness and the clean, bubbling lather. Without it, a soap would be too soft and wouldn't clean as effectively.

Castor oil is added in small amounts for its ability to boost and stabilise lather and harden the bars. A little goes a long way.

Shea butter adds a layer of deep conditioning and gives the finished bar a smooth, creamy feel on the skin.

None of our bars contain palm oil. We've never used it — not because it's trendy to avoid it, but because we don't need it. Our combination of oils does everything palm oil would do, with a better result for your skin and a cleaner supply chain.

Where we add scent, it comes from essential oils or cosmetic grade, certified fragrance oils without harmful chemicals. Some of our bars contain no scent at all, for skin that is sensitive to fragrances.

...One more thing worth knowing

Cold process soap is a living product. It continues to improve as it ages — the bar gets harder, the lather gets creamier, the scent mellows. A fresh bar is perfectly usable, but one that has been cured for six months to a year is actually much better. A well formulated bar can easily stay fresh for 3-4 years.

Store it somewhere dry between uses and it will last a long time. That's another thing commercial bars can't claim.

Ready to try the real thing?

Shop our botanical soaps: https://www.thecurated.ch/collections/botanical-soaps
Shop our milk soaps: https://www.thecurated.ch/collections/milk-soaps