The fundamental recipe for soap is a combination of lye and fat. The fat can be an animal fat or vegetable-based oil, but those are the two primary ingredients. 

When the proper amount of fat and lye is heated it causes the molecules in the fat to bond with the lye molecules, and when allowed to cool it hardens. That hardened combination is what we commonly think of as soap.

It’s unusual for someone to go out and buy some lye and fat to make soap. But in extreme times, you might want to at least know how to make your own. Fat and ashes are common and if you know a bit about how to put them together, you can make soap for general bathing to laundry to just doing the dishes.

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A Bit of Science

Lye is the key to soap making. And it’s dangerous. It has a pH of 13. If you don’t know what that means, it’s all about the pH scale. It runs from 0 to 14 and measures the acidity and the alkalinity of everything. 

Hydrochloric acid is at the 0 end of the scale. It’s scary stuff. But lye lands at the 13 end of the pH scale. It’s just as toxic and dangerous as hydrochloric acid!

Lye is the active ingredient that gives soap its cleaning properties. There are two types:

1. Sodium Hydroxide (NaOH)

The lye that is purchased commercially from a store or online is known as sodium hydroxide. It is a potent chemical and can cause severe burns if it comes in contact with skin, and blindness if it splashes into the eyes and is not immediately treated.

2. Potassium Hydroxide (KOH)

The lye from wood ash is known chemically as potassium hydroxide. It’s less caustic than sodium hydroxide but can still cause injury to both the skin and eyes.

As we get into this process, we’re going to detail how to extract lye from wood ash and then concentrate it. Be careful, and we’ll detail how to do this safely.

As far as the fat component is concerned, things get a little simpler. Pick your fat: bacon fat or lard, beef fat or tallow, and any assortment of oils from olive oil to corn oil. If it has fat molecules, it will properly bond with the next and most important process step.

About Saponification

Saponification is what converts lye and fat into soap. It’s a simple process where the fat and lye are slowly and carefully heated over a period of time. The saponification process binds the fat molecules to the lye. The result is a hard bar of solids that we call soap. We’ll go step by step through the whole process.

Urban Soap Making

Soap making seems like a primitive, pioneer exercise. But anyone can do it. If you have any access to ash and fat, you can make soap. It can be more of a challenge in an urban environment, but if you can burn something to ash (especially wood), you’ll have a fighting chance. 

Ash sources vary but generally the ash from oak, maple, hickory, and even ash trees make the best source of ash for soap making.

If you have a pellet stove, you’re really in luck. The white ash from a pellet stove which is the result of burnt hardwood pellets is one of the best ash sources for soap making.

If you’re depending on ash from a wood stove or fireplace, you have some work to do. You’ll have to run it through a screen to clear out the large bits of charcoal.

In an urban environment you could also use lumber, but don’t use any treated wood. The chemicals won’t completely burn off, and the last thing you want is a bar of soap saturated with harsh, water-repelling chemicals.

In a real pinch, you could even burn newspapers and magazines to create a source of ash.  It may take longer to concentrate the lye derived from paper sources to get to a pH of 13, but if it’s all you have, it can work.

Ash 101

You don’t want chunks of charred wood or charcoal in your ash harvest. You want pure, white ash and nothing more as much as possible. What you’re eventually going to do is percolate water through the white ash to draw out the lye in the ash. 

Do what you can to pulverize the ash and filter it through a screen.

You can buy lye online, but in desperate times, it’s wise to know how to make your own.  But be forewarned that lye is highly toxic, and as you distill and concentrate the lye from your ash collection, it will become a somewhat dangerous distillation.

Regardless of where you harvest your ashes, it’s best to screen them. Use a wire mesh or screen. You’re just trying to get rid of those clumps and lumps of charcoal and bits of cold coals. You just want powdery, fine ash.

There are various steps to the process requiring a basic collection of equipment, tools and supplies. 

Equipment:

Tools:

• A drill with a 1/2 -inch drill bit
• A large ladle for pouring the soap into molds

Supplies (ingredients):

• A large bucket of ash preferably from a hardwood fire and ideally from a pellet stove.
• Fat or oil. You could render pork fat into lard, beef fat into tallow, or use any type of vegetable or seed oil. 
• Gravel and straw to keep the ash from mixing into the lye while it percolates through the bucket
• Soft water with few or no minerals. Rainwater is best.
• Kosher salt (optional). Adding salt makes a harder bar of soap and coarse kosher salt will act as an exfoliant if added towards the end of the process.
• Parchment paper to wrap your soap bars or aluminum foil.

Adding Herbs, Fragrances or Essential Oils

• Many soaps have a fragrance, and you can create your own using either herbs; rinds from lemons or oranges and fragrances derived from essential oils. 
• You’ll want to chop the fresh herbs or zest the rinds from the oranges. With essential oils a few drops will do. 
• Lemons, limes and oranges are popular citrus rinds for adding fragrance to soap, and lemon balm, mint, lavender, rosemary and thyme are the most commonly used herbs. 

The Ash to Lye Distillation Setup

This isn’t hard to do. All you’re trying to accomplish is creating a setup to allow water to slowly percolate through ash and release a weak lye solution into a pot.

It starts with a 5-gallon bucket with a hole drilled in the bottom about the diameter or your thumb. This 5-gallon bucket is then set on top of a large stainless-steel pot. 

Don’t use an aluminum pot! The lye will erode the aluminum. It has to be stainless steel, although our pioneer ancestors sometimes used cast-iron. Use what you have, but just don’t use an aluminum pot.

There are some layers to put into your 5-gallon bucket. Start by putting some straw at the bottom topped with some gravel. Layer some more straw or dry grasses over the gravel about 3 inches thick. You then fill the bucket with your ash but leave about 3 to 5-inches of headspace at the top.

You then pour boiling water into the top of bucket over the ash. As the water percolates through the ash, continue to add more boiling water. Be patient. This can take hours and even days. Continue to leach the lye out of the ash until your stainless steel pot is about half full. You’re now ready to concentrate the lye.

Reducing the Lye

This is where things get a bit dangerous. You want a low and slow fire. You don’t want a pot of bursting and bubbling lye. The idea is to evaporate the water carefully and reduce the lye to a pH of 13. 

Make sure you wear eye protection, leather gloves, a long-sleeve shirt or jacket, and a face mask is also a good idea. As the lye concentrates, it will become more corrosive.

When you get to a pH of 13 with your concentrated lye, remove the pot from the heat and let it cool completely. Stay cautious. Even when cool, the lye can cause blisters or worse. 

Saponification 101

To start the soap making process, you need to start with an empty 5-gallon stainless steel pot. Here are the specific steps and proportions:

1. For 2 bars of soap, measure 1 cup of hot fat and set aside.
2. Bring 3/4 cup of the concentrated lye to a medium boil in a stainless-steel stockpot and slowly add the fat stirring as you go. To make more soap, scale up the amounts of lard and fat proportionately and use a larger pot.
3. DON’T ADD THE LYE TO THE FAT. It will splatter. Always add the fat to the lye.
4. Add a ¼ teaspoon of salt if you want a harder soap.
5. Continue to boil the mixture stirring constantly for 3 minutes until thick like porridge with no chunks.
6. Reduce the heat to keep warm around 100 degrees Fahrenheit.
7. Stir the mix for a minute and then let the mix sit for 10 minutes and stir again.
8. Repeat this gradual heat and stir every 10 minutes until the soap batter turns a golden brown. The color can vary depending on the type of fat and the purity of the ash you used for the lye. This part of the process can take hours so be patient. It can also happen faster.
9. To determine doneness, lift the soap solution from the pot with a ladle and look for a long, steady stream. This is called a “trace test” and is a good indication that saponification has occurred.  

10. At this point you can mix in your chopped herbs or citrus rings or essential oils to lend a fragrance and exfoliant properties.

This is also when you could add coarse kosher salt to act as an exfoliant.

Creating the Soap Bars

Once your soap has fully saponified and after you’ve added any fragrances, you’re ready to make your soap bars.

Cupcake tins are an easy option but if you want a bar of soap that actually looks like a bar or soap, you can make a mold out of cardboard or buy the molds on Amazon. 

The cardboard mold will essentially give you a large brick of soap as long and deep as your mold. Once it has hardened, a large chef’s knife can be used to simply slice the brick into the sizes you want. 

Curing the Soap Bars

Homemade soap bars need to harden and cure. This usually takes a week or two. The bars should be placed on a tray or board lined with parchment paper and left to dry or cure in a protected space like a closet or pantry shelf. The garage can work in a pinch, as long as they’re not exposed to the sun or rain. 

Soap Packaging

The easiest way to package your homemade soap is to wrap the bars in parchment paper or aluminum foil. You could also store them in plastic bags or even plastic containers with lids. All you’re trying to do with packaging is preventing any ambient humidity from degrading the soap.

Homemade Soap Shelf Life

Soap generally has a long shelf-life if properly packaged and stored. Figure you’re homemade soap will be stable for 2 to 3 years. Maybe longer. 

As time goes on, you may find it gets a bit hard around the edges, but water in a bath or shower goes a long way to keeping soap sudsy and stable. If you find it’s not working like it once was, start a fire and find some fat. After that, you’ll know what to do.

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