How to Make Soap: A Beginner’s Cold Process Guide

Walk through any farmers market or craft fair this summer and you will find tables stacked with handmade soap in every color and scent, each bar built from little more than oil, water, and lye. Making your own is easier than it looks, and it ties you to a craft people have practiced for nearly 5,000 years. Here is how to make soap with the old-fashioned cold process method, along with the strange, sudsy history behind the bar in your shower.

Soap is a $22 billion industry worldwide, and 13 billion bars are sold in the U.S. every year. Most of that is mass-marketed, but there is a growing market for handmade soap at farmer’s and craft markets across the country. Recent reports count 300,000 soap-making businesses in the US, with the artisan and homemade soap market bringing in $150 million per year. Some of those makers started right where you are now, at the kitchen counter with a single recipe.

A Dirty Past

For a long stretch of human history, people had little notion of personal cleanliness. Medical leaders once believed it was unhealthy to clean the body with soap at all, so the bar we take for granted had to earn its place slowly.

The earliest evidence of soap goes back to the ancient Babylonians in 2800 BC. Archeologists discovered cylinders inscribed to say “fats boiled with ashes,” and assumed this was the basis for the product. In ancient Egypt, a medical document called the Ebers Papyrus described a recipe of animal and vegetable fats and alkaline salts used for washing. That combination of fat and alkali is still the heart of every bar today.

According to legend, it was common in ancient Rome for animals to be sacrificed on Mount Sapo, the Latin word for soap. Rainwater would mix with animal fats and ashes, which provided the alkali, around the ceremonial altars and run down to a river where women washed clothes. They found the mixture helped clean textiles, and the concept was born for both laundry and personal care. The tale of Mount Sapo is often told but has never been proven, so we file it under good folklore rather than settled fact.

These early soaps, common to the communal baths used by the Greeks and Romans, were likely brown or gray, soft, and unscented. Even so, they were a big improvement over the washing habits of the day. Bathers were accustomed to rubbing their bodies with clay or pumice and scraping the mixture off with a stigell, a curved, trowel-like instrument.

The use of cleansing soaps then waxed and waned for a time. Making it was considered an art in Italy, Spain, and France, where a purer, softer, milder castile soap was formulated. In the Islamic Middle East, more sophisticated soaps were made using olive oil and exported to Europe. These small batches were reserved for the wealthy, while less well-to-do families passed their own soap-making recipes down through the generations.

In the Middle Ages, medical experts began to think bathing helped spread illness. This frightened France’s King Louis the 14th, who is said to have taken only three baths over a lifetime, apparently covering his body odor with perfumes. Thankfully, medical opinion changed. By 1800, French chemist Nicholas LaBlanc figured out how to use common salt in the manufacturing process, which paved the way for soap to become one of the first mass-marketed products.

Soap to the Rescue

The understanding of soap’s benefits to fight infection and promote healing grew through several events of the 19th and 20th Centuries. During the Crimean War in the 1850s, Florence Nightingale, credited with the evolution of modern nursing, stressed the importance of washing hands with soap to prevent the spread of cholera. The U.S. Civil War launched the business of William Proctor and James Gamble, who built fortunes on their soap products.

An American folklore grew up around the image of rural families mixing animal fat and lye made from ashes to produce their own soaps. That self-reliance no doubt influenced the emergence of soap-making hobbyists and the thriving boutique businesses putting their own spin on the practice. Go to any farmer’s market or specialty shop, and on FarmersAlmanac.com, and you will find a dizzying variety of fragrances, colors, and textures.

And that leads us back to the Brits and the American Revolution. For nearly 150 years, England imposed a healthy tax on soap to help fund its wars abroad, including those in the New World. A tax that tripled the cost of a bar might well have been as offensive to colonists as the fees placed on their warm beverage of choice. We are taught about the Boston Tea Party from elementary school on, but the revolutionaries could have brought their tax dissent to a sudsy conclusion instead. England lost its hold over the soap industry by the 1850s thanks to factory production, and by their actions the colonists proved they could better afford to hoist a shipment of tea into the harbor than to give up their baths.

The Three Main Ways to Make Soap

Before you gather supplies, it helps to know which road you are taking. Home soap makers generally use one of three methods, and each asks for a different level of comfort with lye.

• Cold process: the traditional route below. You mix your own lye solution with oils and let the bars cure for several weeks. It gives you the most control over ingredients and is the method the recipe here uses.
• Melt and pour: the beginner-friendly option. You buy a premade soap base, melt it down, add color and scent, and pour. No handling of raw lye, which makes it a good first project for kids and cautious first-timers.
• Hot process: a cousin of cold process that cooks the batch with added heat, usually in a slow cooker. The bars are usable sooner but come out more rustic in texture.

If the idea of measuring lye makes you nervous, start with melt and pour and work your way up. When you are ready for the real thing, the cold process recipe below is the one artisans have relied on for generations.

How To Make Soap

Popular with artisan soap makers and DIY hobbyists, the old-fashioned cold process uses several types of vegetable oils and a lye-water mixture. The basic recipe can be mixed with an endless variety of fragrances and colors to make the soap your own. Michigan State University Extension offers a plain-English overview of home soap making if you want to read up before you begin.

Self-proclaimed Soap Queen Anne-Marie Faiola, founder of the crafting company BrambleBerry.com in Bellingham, Washington, shares the basic step-by-step process in the following video:

Faiola constantly stresses the importance of safety when working with sodium hydroxide lye, which is a corrosive substance. She says to wear protective eyewear, rubber or plastic gloves, and long-sleeve shirts and pants to protect against splashing. Work only in a well-ventilated room, since the lye mixture produces dangerous fumes.

Ingredients:

• 7.9 ounces of distilled water
• 3.4 ounces of sodium hydroxide (lye)
• 8 ounces coconut oil
• 8 ounces palm oil
• 8 ounces olive oil

Tools:

• Heat-safe nonreactive containers and utensils
• Immersion stick blender
• A soap mold, plus goggles and gloves for safety

Directions:

1. Measure the distilled water and lye into two separate containers.
2. Add the lye slowly to the water, which creates heat. Carefully set it aside to cool.
3. Heat the oils as needed to get them into liquid form and within 10 degrees of each other.
4. Slowly pour the lye water into the mixed oils.
5. Use the stick blender to mix the ingredients, avoiding air bubbles, until the mixture shows faint trailings, called trace. Add any fragrances or colors when the mixture is the consistency of light pudding.
6. Pour the liquid into a mold.
7. In 1 to 3 days, remove the soap from the mold, slice it into bars, and cure them in a cool, dry place for 4 to 6 weeks before using.

Choosing Your Oils, Scents, and Colors

The base recipe is a starting point, not a rule book. Each oil brings its own quality to the finished bar, and once you understand what each one does, you can adjust the batch to suit your skin and your kitchen.

• Coconut oil gives a hard bar and a big, cleansing lather.
• Palm oil adds hardness and a stable, creamy lather. Look for a sustainably sourced label if that matters to you.
• Olive oil makes a gentle, mild bar, the same quality that made old-world castile soap so prized.

Swapping oils changes the lye amount you need, so run any substitution through a lye calculator before you pour. For scent, add skin-safe essential or fragrance oils at trace. For color, natural clays, cocoa powder, and dried botanicals all work, or you can leave the bar plain and let the ingredients speak for themselves. If you would rather clean without lye at all, our guide to the many household powers of vinegar covers a gentler route.

Keep Learning

See more soap-making tutorials on YouTube here.

Join The Discussion!

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How to Make Soap: Frequently Asked Questions

Is it safe to make soap at home?

Yes, as long as you respect the lye. Sodium hydroxide is corrosive, so wear goggles, gloves, and long sleeves, work in a well-ventilated room, and always add the lye to the water rather than the other way around. Keep children and pets out while you work. If you would rather skip raw lye entirely, use the melt and pour method with a premade soap base.

What is the cold process method?

Cold process is the traditional way to make soap from scratch. You combine a homemade lye-water solution with vegetable oils, blend to trace, pour into a mold, and let the bars cure. It is the method in the recipe above, and it gives you the most control over what goes into the bar.

Do I have to use lye to make soap?

All real soap is made with lye, because the reaction between lye and oil, called saponification, is what turns fat into soap. The good news is that no lye remains in a properly cured bar. If you do not want to handle raw lye, choose a melt and pour base, where the saponification has already been done for you.

How long does homemade soap take to cure?

Remove cold process soap from the mold in 1 to 3 days and slice it into bars. Then cure the bars in a cool, dry place for 4 to 6 weeks before the first wash. Curing lets extra water evaporate, which gives you a harder, longer-lasting, milder bar.

Can I substitute the oils in the recipe?

You can, but each oil needs a different amount of lye to saponify, so a swap changes the whole balance. Run any change through a lye calculator before you pour, and adjust the sodium hydroxide accordingly. Coconut oil hardens and cleanses, palm oil adds a stable lather, and olive oil keeps the bar gentle.

Did England really tax soap?

It did. For nearly 150 years, England imposed a tax on soap to help fund its wars abroad, and it could triple the cost of a bar. England lost its grip on the soap industry by the 1850s once factory production took over. The tax on soap rarely gets the attention the tax on tea does, but it hit colonists just as hard.