The Truth About Lye: Saponification and Natural Soap

The Truth About Lye: Saponification and Natural Soap

Making all-natural cold process soap is part science, part art, and 100% carefully-chosen ingredients.

Face, hands, body — few products are as intimate with our bodies as soap.

For something used daily on our skin, the processes and ingredients needed to make soap are quite misunderstood. “Saponification” and “superfatting” certainly do not roll off the tongue, and we’ve been told that “lye” should be avoided at all costs. 

However, natural soap-making involves both time-tested techniques and ingredients. Written recipes for soap date back almost 5,000 years to ancient Babylon, and though refined over time, the basic premise (encouraging fat or oil to undergo a chemical reaction) remains the same.

At Marmelo, we believe in using the best botanic ingredients to create nutrient-rich, all-natural products, and we’ve chosen to make soap the way we do to enhance those ingredients as well as support your skin. After all, the best ingredients need the best processes: minimal, intentional, inspired by nature.

What is saponification, and what is the role of lye in soap-making? Let’s explore the world of natural soap and clean up any soap misconceptions. 

What is saponification?

Natural, cold-process soap is made possible by a process called saponification. Meaning "conversion into soap," saponification is a chemical reaction in which triglycerides found in fat or oil react with sodium hydroxide (lye) to form soap. 

As you may remember from high school chemistry, when an acid and a base combine, they neutralize each other to create a salt. During saponification, fats or oils (fatty acids) come into contact with sodium hydroxide, a strong base. The fats react with sodium hydroxide and are converted into soap (a fatty acid salt) and glycerin, a natural emollient that occurs during saponification.

Triglycerides (oils/fats) + sodium hydroxide (lye) = soap + glycerin

It takes approximately 24 to 48 hours to complete once the lye and oils have been mixed and poured into a mould. Saponification can be sped up by adding heat (“hot processing”) or slowed down by keeping it cool (“cold processing”).

Lye and natural soaps

Fat and water are both needed to create soap, but as we know, oil and water are difficult to combine. That’s where sodium hydroxide — aka lye — comes in.

Truth time: you cannot make real soap without using lye. But that does not mean there is lye in your soap.

Lye (sodium hydroxide = NaOH) is a non-organic chemical that is a product of the electrolysis of salt (running an electric current through saltwater). Today it is commercially made, but traditionally soap was made using hardwood ash from cooking fires mixed with animal fat and water, and lye was created by water seeping through the ashes.

In soapmaking, lye binds oil and water together. During saponification, the fats or oils break down into fatty acid chains while the lye is neutralized.

Remember: lye is only dangerous in its virgin form and during the first stage of curing before it has completely neutralized. Once the soap has cured for 24 hours, there is no lye remaining in the soap, as it has been completely used up in the process of combining oil and water.

However, it is very important to use precise measurements and ratios of ingredients to ensure no lye remains in the final product. At Marmelo, we prefer to “superfat” our soaps to make sure our natural soap is not only lye-free but also luxurious and moisturizing.

Ever heard of superfatting? We’ll break down the basics of saponification below.

The basics of saponification

Hot vs. cold processing 

There are two main methods for creating natural soaps: hot process and cold process. 

For the hot process method, the ingredients are mixed to begin saponification, poured into a mould, then “cooked” in a double boiler or oven. The addition of heat speeds up saponification, meaning that hot process soap can be used immediately after cooling. However, heating the mixture can alter the ingredients in the soap, such as decreasing (or even destroying) nutrients found in the oils.

With the cold process method, no additional heat is used. When lye encounters water, it causes an exothermic reaction (the reaction gives off heat), and this heat is what causes saponification to occur. Cold processing requires a longer cure time to allow the water to slowly evaporate and also gives the soap a longer shelf-life than hot processed soap.

In the Marmelo small-batch laboratory, we prefer to make cold process soap, as we believe this is the best way to preserve the integrity of our carefully-chosen ingredients. For our naturally-scented soaps, cold processing allows us to protect the scent (and any nutritive benefits) of botanical oils such as eucalyptus or lavender, which can be damaged or burned off in hot process soapmaking.

“Superfatting”

To avoid any issues with lye, as well as to create a more moisturizing product, many soapmakers choose to “superfat” their soaps. 

Superfatting is the process of adding extra fats (oils or butters) when formulating natural soap — this means there is more fat in the mixture than the lye can react with during the chemical reaction. These extra fats are left unchanged by the saponification process, and therefore provide more moisturizing properties to the soap.

Different types of oil require different amounts of lye to turn them into soap. If you use exactly the required amount of lye needed for your oil or fat type, you’ll create a soap that is 0% superfat. That “squeaky clean” you sometimes feel is likely from a soap that is 0% superfat — it cleans so well that it has the potential to dry or irritate the skin. 

Superfatted soap is not only more moisturizing and emollient for the skin, but it also allows us to be confident that we have created a product with lye completely removed. Think of it as a "soap insurance policy."

Curing time

Finally, natural cold processed soaps are left to dry, or cure, for approximately four to six weeks. The first 24 to 48 hours of curing time allow the saponification process to complete and then the soap can be unmolded, and over the following weeks, any excess water continues to evaporate out of the soap. During this time the soap is "perfected" becoming harder and longer lasting.

While curing, the soap is kept in a cool and dry location (we don’t want moisture to linger in or on the soap). As time goes by and water evaporates, the soap restructures into the smooth, solid consistency you know and love in natural cold processed soaps. 

When soaps contain any fragrant plant oil compounds, we take care to cure each soap apart from other soaps so that the scents do not mix.

Cold processed soaps

At Marmelo, all of our soaps are cold processed from scratch, just how grandma did "back in the day"! We craft in small batches, using organic and wildcrafted ingredients whenever available. 

Our soaps are customized for various uses and skin conditions. You will notice varying superfat levels for added protection and healing benefits and degree of moisturizing properties. The various botanical extracts chosen in our recipes are formulated for synergy for specific desired effects. All oils have varying saponification values and effects when in soap and we adjust and perfect our recipes to make a soap softer or harder for instance or creamier or sudsier. Read our soap descriptions carefully to find your dream soap!

For sensitive skin, our gentle maligne soap uses glacial marine clay and Moroccan chamomile (blue tansy) for an antioxidant-rich and nourishing lather. Its creamier than most with anti-inflammatory properties, Maligne helps soothe and calm both body and mind.

A spa-like experience awaits with the rosetta soap, a salt bar designed for gentle exfoliation to reveal your natural glow. Relax, recharge, and reinvigorate your skin with Himalayan pink salt, sea salt, eucalyptus oil, and lavender oil.

All-natural cold processed soaps are amazing for the skin as they pose less of a risk for irritation compared to soaps containing synthetic chemicals or that are detergent bars (most that are commercially available today). There are no perfumes or synthetic additives of any kind in our cold processed soaps. However, that doesn’t mean that using natural oils or plant extracts doesn’t pose a potential risk. Everyone’s skin is different, and there’s always a possibility of allergic reactions. 

As with any skincare product, we recommend testing a little on your arm before general application. If you notice redness or irritation, stop using it right away. Get emergency help if you experience swelling or hives.