Do you want to learn how to make soap from scratch? Cold process soap making method is what you’re looking for, friend! I’m super excited to introduce you to soap making from scratch, with this ultimate guide to cold process soap making for beginners.
From tools and ingredients, to soap making science, safety, and common questions, this guide will walk you through everything you need to know about making soap from scratch, using the cold process soap making method.
A note before you read on: It’s easy to get overwhelmed when you’re a new soap maker. As you read this guide, you may feel like there’s so much to learn, so many supplies you need to gather, so many safety rules to remember…
The whole soap making process seems daunting. But I’m here to reassure you, you can do this!
This post contains affiliate links. As an Amazon Associate I earn from qualifying purchases. This means I may receive a small commission—at no extra cost to you—from any sales made through these links. I only recommend products that I personally use and love!
How Do You Make Soap from Scratch?
You make soap from scratch by blending together:
- Liquid: water, goat’s milk, beer, etc.
- Oils or fats: coconut oil, olive oil, tallow, etc.
- A caustic: sodium hydroxide (AKA lye) for solid bar soap, potassium hydroxide (AKA caustic potash) for liquid soap
The lye is first dissolved in the liquid, then is blended with the oils to create soap.
Simple Soap Chemistry
When lye is mixed with oils, it triggers a chemical reaction called saponification.
Fat or oil molecules, called triglycerides, are made up of glycerin and fatty acids. When these molecules are mixed with a caustic (lye) the bonds holding the molecules together break, leaving you with glycerin and salts of fatty acids, or what we commonly call soap.
Saponification is the chemical act of turning a caustic, fats, or oils, into soap.
Without all of the modern conveniences that make soap making today much easier (like electric stove tops, and ingredients that can be bought rather than made) soap making was a long and arduous process.
Quick Soap Making History
Our foremothers and forefathers would typically make soap only once a year, cooking the water, oils, and lye made from wood ash together in a big vat over an open fire.
Wood ash lye (also called potassium lye) first had to be made by mixing hardwood ash with rainwater, allowing the lye to leach out over time. This lye water was captured in a bucket and collected to make soap.
Side note: If you’re super interested, get the down-and-dirty details of making wood ash lye from scratch from this article by The Spruce Crafts. But no need to go that far today. You can purchase lye at any online soap making supplier.
Fats and oils also needed to be collected and prepared for soap making. Soap was made from whichever oils or fats were readily available.
In the U.S., animal fat was historically used to make soap. Women would save all the fat from their meat, render it down into tallow which they saved up to make their soap. In other parts of the world, vegetable oils, like olive oil, was used to make soap.
Because they had no accurate way to measure the strength of their lye, old time soap was often very harsh and lye-heavy.
Today’s scratch-made soap is supremely gentle and good for your skin, thanks to modern tools, ingredients, and knowledge.
I imagine that our ancestors would be shocked to learn that today, we make soap just for fun!
And soap making is fun. It’s a chance to get creative as well as end up with a really gentle, luxurious, and useful product. A far cry from the old time soap the pioneers made.
What Is Cold Process Soap?
There are three different ways to make homemade soap from scratch. They are:
- Cold process soap method
- Hot process soap method
- Melt and pour soap method
The Hot Process Soap Method
Our ancestors made soap using the hot process method.
With the hot process method, lye, liquid, and oils are cooked on the stove top until the saponification process (the process of turning oils and lye into soap) is complete.
Hot process soap making is so named because you use heat to make the soap. After cooking, the lye/water/oil mixture (or what soapers call the “soap batter”) is very thick, like mashed potatoes. This is because most of the water has evaporated out during the cooking process, leaving a pot full of not-quite-solid-yet soap.
The cooked soap batter is spooned and squished into a soap mold, left to cool and firm up for a day or so, then removed from the mold and sliced into bars.
The Cold Process Soap Method
The cold process soap method uses the same ingredients as hot process soap: lye, water, and oils. The difference is, with cold process soap the oils are initially heated to melt but the ingredients are not cooked further. They’re left “cold.”
Instead, after mixing the ingredients together they are poured into a soap mold and left alone. The saponification process happens in the mold without any extra help from us.
Some people call this method cold press soap, which is a misnomer and probably because they misheard the word “process.”
Today, the cold process method is the most popular way to make soap from scratch.
It’s popularity is two-fold. First, you don’t have to babysit a cooking soap batter.
Secondly, cold process soap batter is quite fluid. If hot process soap batter is like mashed potato consistency, cold process soap batter is like pancake batter.
The thin batter of cold process soap is easy to work with, and allows the creation of gorgeous swirls.
Also, the end result gives you soap bars with a smooth, even consistency, unlike hot process which produces more craggy and rustic-looking finished soap bars.
The soap is removed from the mold after 24 to 72 hours, and cut into bars. Cold process soap bars are actually quite soft and sticky, similar to a soft cheese, when first unmolded. This is because they still contain lots of excess water.
Remember how the water evaporates out of hot process soap while cooking? With cold process soap the water evaporates out during a process called cure. (We’ll talk more about cure in just a bit, so keep reading.)
The Melt and Pour Soap Method
The last soap making method is also the simplest. With the melt and pour method, you aren’t making soap completely from scratch with oils, liquid, and lye. Instead, you melt down a premade soap base and add your choice of color, fragrance, herbs, etc.
If cold process soap is akin to making a cake from scratch, melt and pour soap is like making a cake from a boxed mix.
The benefit to melt and pour soap making is you don’t have to handle lye yourself. The drawback is because the base is already made for you, it isn’t technically making soap from “scratch.”
Also, while there are bases that contain only naturally-derived ingredients, no melt and pour soap base is completely natural.
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Cold Process Soap Benefits
There are plenty of benefits to making your own cold process soap. Some of the biggies are:
You have complete control over the ingredients in your soap. Craft soap your way. Make it all-natural, eliminate synthetic ingredients, and avoid any ingredients you’re allergic to. You can also tailor soap to your taste in color, fragrance, and appearance.
Handmade soap is gentler than store-bought detergent bars. When crafted properly, cold process soap is supremely gentle, and works well for those with sensitive or problem skin.
Handmade soap is more moisturizing than detergent bars. Remember, salts if fatty acids and glycerin is created when soap is made. It’s the glycerin that makes handmade soap so much more moisturizing than detergent bars or commercially-made soap.
You’ll save money making your own homemade soap. If you’re already a handmade soap convert, you know that a good bar of handcrafted soap isn’t cheap, with most good bars costing between $6 and $12. You can make your own soap and save some cash.
One thing to realize, though, is you aren’t going to save money making your own soap if you’re currently buying inexpensive detergent bars for $.99. Your handmade soap will still cost more, but you’re comparing apples and oranges!
Compare the cost of your handmade bar to other what handcrafted soap is selling for to see the true cost savings.
It’s a fun craft that’s useful too! If you’re a crafty or artistic person by nature, and you also like practical crafts, soap making is the hobby for you! You can be artistic and create something that’s useful too. And when you use it all up, you get to make more.
Drawbacks of Cold Process Soap Making
There are some drawbacks to making cold process soap. They are:
Your soap takes 30 days or longer before it’s ready to use. Surprised? It’s true. Although you can make up a batch of soap in an hour or so, it needs to cure for 30 days before use. (You’ll get all the info on why and how to cure your soap in just a bit.)
You must handle lye. I went back and forth deciding to call this a drawback, because you can handle lye safely and it’s really not as scary as it seems. But in some cases, handling lye really is a drawback—like if you have small children. It doesn’t have to be a deal breaker, you just have to be aware of and follow all lye safety guidelines.
Handmade soap bars dissolve away faster than store-bought detergent bars. It’s the glycerin again! Glycerin in the soap bar attracts water from a humid bathroom air, or a wet soap dish, and can leave you with a gooey glop instead of a bar of soap if you’re not careful. Keep handmade soap dry between uses.
Certain colors, fragrances, and ingredients morph in cold process soap. Due to the high pH of cold process soap batter, ingredients can do weird things! Colors change completely, fragrances disappear into nothing, fresh ingredients turn a funky shade of brown or grey.
To avoid this, use colorants and fragrances that are tested and labeled for cold process soap use.
You can’t make a transparent soap with the cold process method. The cold process method makes a lovely soap, but it’s always opaque. If you want a transparent soap you must use melt and pour, or a (fairly complex) variation of the hot process method.
Still, the benefits of making your own luxurious handmade soap far outweigh the drawbacks. I’ve been making my own soap for 20+ years and will never go back to store-bought!
Cold Process Soap Making Ingredients
Are you ready to dive deeper into the ingredients you need to make soap from scratch? You need just a few simple ingredients to get started: water (or another liquid like goat milk), oils, and lye.
Oils and Fats
Oils make up the bulk of your handmade soap. When it comes to soap making, you can use nearly any oil or fat (animal or vegetable) that strikes your fancy.
When choosing oils, a good rule of thumb to remember: solid at room temperature oils (like coconut, palm, lard, or shea butter) will produce a harder finished bar of soap. Liquid oils (sweet almond, sunflower, olive) produce a softer bar.
Most soap recipes use a blend of solid and liquid oils to produce a bar that lathers well, is cleansing without being drying, and doesn’t melt away too quickly.
Staple soap-making oils are:
Coconut oil: This oil makes a hard, white bar of soap that lathers exceptionally well, with big, fluffy bubbles. The majority of handmade soap contains some coconut oil. Coconut oil can make make a drying soap, so it’s generally used along with other oils.
Palm oil: Palm also produces a hard bar of soap with lots of lather. It isn’t as drying to the skin as coconut oil can be. The drawback to this oil is that the agriculture and harvest of palm oil is endangering orangutan habitats. Many soapers eschew this oil because of this. If you choose to use palm oil, a more environmentally-friendly option is to buy only responsibly-sourced palm oil, identified by the Roundtable of Sustainable Palm Oil (or RSPO) certification.
Olive oil: Olive oil makes an exceptionally mild and moisturizing bar of soap. Castile soap is traditionally an olive oil-only soap, but most soap makers blend olive oil with another oil. Olive oil alone produces a low, creamy lather. But it produces a much softer bar, and one that needs a long cure time. Blending with another hard oil helps temper this.
P.S. Buy the cheap olive oil, it works just as well as the “good stuff” for making soap.
Castor oil: Castor oil, in my opinion, belongs in every handmade soap bar. It creates a fluffy, luscious lather that feels great on the skin. It also has skin conditioning properties. You won’t need to use too much of this oil, though. Just 5% of the total oils will do, as too much can leave a sticky residue on the skin.
Lard or tallow: Even today, lard (from pork) and tallow (from beef) are very common soap ingredients. These animal fats make very hard, white, long-lasting bars of soap. Tallow especially creates big, fluffy lather. Lard soap lathers well, too, but some find the lather a bit slimy feeling. Blending it with another oil helps counteract this.
Besides the chief soap making oils which make up the bulk of your soap recipe, you can also add specialty oils to your soap.
These oils are more expensive than the aforementioned oils so they are used in smaller quantities. But they give your soap added benefits to make that recipe POP.
Specialty oils often used in soap making include:
- Sweet almond: Conditioning, moisturizing, fluffy lather
- Sunflower: Conditioning, moisturizing, rich lather
- Shea butter: Moisturizing, can be a lather-inhibitor
- Cocoa butter: Moisturizing, makes a hard bar of soap
- Mango butter: Moisturizing, makes a hard bar of soap, creamy lather
- Apricot kernel: Gentle cleansing, moisturizing
- Avocado: Gentle cleansing, moisturizing
- Hemp: Gentle cleansing, creamy lather
Of course, these are just a few of the options you have. You can make soap with any type of oil imaginable (with the exception of mineral oil, baby oil, and the like. These are petroleum oils, not triglycerides, so you can’t turn these oils into soap.)
MY RECOMMENDATION: There’s no need to spend a ton of money on oils when you’re first starting out. All you need are just three good basic oils:
With these three oils you can make a heck of a nice bar, and they’re relatively inexpensive. Once you’re feeling comfortable, you can branch out and start experimenting with other oils.
Sodium Hydroxide (AKA Lye)
Are you nervous about making soap from scratch because of they lye? Don’t worry, friend.
Although lye sounds scary, if you use some simple and common-sense safety precautions there is no reason to fear it. In all my years of soaping, I’ve never had a frightening incident with lye; I’ll venture to guess most soapers can say the same.
If you can use bleach or drain cleaner in your home safely, you can use lye safely too.
When choosing lye, you must only use 100% pure lye. Lye is a drain cleaner (I know, yikes!) but it’s also used in the curing of olives and the manufacture of bagels.
Buy lye from a soap making supplier, rather than a hardware store, to get pure lye that is not adulterated with other harmful ingredients.
MY RECOMMENDATION: 100% Pure Lye from Essential Depot
Can You Make Soap from Scratch Without Lye?
No, soap cannot be made without lye. Lye is a necessary ingredient to turn oils into soap. There is no substitute for lye in soap making.
While soap itself can’t be made without lye, there is a way to make soap without handling lye yourself. Remember the melt and pour soap method from earlier? The manufacturer makes the soap base with lye. All you have to do is cut it, melt it, and pour it into the mold.
The drawback to melt and pour soap is you don’t have complete control over the ingredients, and melt and pour soap bases are not 100% natural (although there are naturally-derived soap bases available.)
But I Don’t Want Lye In My Soap!
You can’t imagine rubbing anything with lye in it over your skin. Neither can I, actually.
Luckily, through the magic of chemistry, when cold process soap is made properly, you DO NOT have lye in the finished product. The oils, water, and lye have changed so that they are no longer oils, water and lye—it’s soap!
No lye is left in properly made finished soap.
With a properly formulated, trusted recipe, your finished soap will not contain a trace of lye. (Read on and I’ll share some of my favorite, properly formulated soap recipes perfect for beginners.)
How To Safely Work With Lye
Maybe you’re still a bit scared of the whole lye thing. That’s OK, friend! I was scared of making soap with lye the first time too.
I’m committed to helping you become comfortable handling lye and making soap from scratch. So, I’ve put together a series of posts to help you understand lye, its important role in soap making, and those all important lye safety rules.
These articles REQUIRED READING before making your first batch of soap:
- 8 Common Questions About Soap Making With Lye
- 7 Must-Know Lye Handling Safety Rules
- How To Neutralize Lye Spills When Making Soap
What Supplies Do I Need to Make Soap?
You will need several specific tools to build your soap making supply kit. Luckily, you can find everything you need at your local big box store like Target or Walmart, or can be bought online.
One important note: All of the supplies are exclusively for soap making. Don’t reuse them for cooking.
This is especially true for the container that is used for the lye water solution.
Mark all of your soap supplies. I use a permanent marker and write SOAP on all of my soaping tools, and LYE on measuring cups and pitchers used for lye. That way an unsuspecting visitor won’t accidentally use my lye solution pitcher to mix up a batch of lemonade.
Alrighty, friend, so here are the soap making supplies you’re shopping for.
Eye Safety Glasses
First and foremost, you need to get yourself some safety equipment. Wear them the entire time you’re making soap, from beginning until after clean up. Don’t make soap without them!
Eye goggles protect your baby-blues (or browns, or greens, or hazels) from lye splashes and soap batter splatters. Buy something that you’ll be comfortable in, that fit well, don’t slip down your nose or squish into your cheeks, and won’t fog up.
Eye glasses won’t give you the same amount of protection; there are protective eye goggles that are designed to be worn over your glasses, so that you can both protect your eyes and see.
Gotta protect those hands too! I use nitrile exam gloves, because they’re thin and I can feel what I’m doing. If you’re allergic to latex, you can use these without problems.
While I personally find them a bit clumsy and cumbersome, I know plenty of soap makers who love rubber dish washing gloves. The benefit of these is they are reusable; just wash your hands well with soap while you’re wearing them, rinse, remove, and let dry.
Stainless Steel Pot
This is what you will use to melt your oils and mix up your soap batter.
This pot must be stainless steel—absolutely no aluminum, cast iron, or non-stick (Teflon) coated pots. These elements react with lye, can throw off toxic fumes and curdle your soap batter.
Check the bottom of the pot. Stainless steel is marked by a stamp on the bottom. An 8-quart sized stainless steel pot is perfect for beginners, and will hold up to 5 lbs. of soap batter.
MY RECOMMENDATION: Cuisinart 8-quart stainless steel pot (I’ve had this workhorse for a decade-plus and it’s still perfect.)
Stick Blender (AKA Immersion Blender)
Stick blenders quickly and thoroughly emulsify your oils and lye solution together and bring it to “trace” (a thickening of the soap batter and the beginning of the soap making chemical reaction.)
Yes, technically you can mix your oils and lye solution together by hand but it takes forevvvvvver to adequately emulsify. It can take more than an hour of constant stirring by hand for some soap recipes to come to trace, compared to 5 minutes or less with a stick blender. So, yeah, you’ll want a stick blender.
Also note that you CAN’T use a hand mixer or regular blender; it is dangerous to use these to make soap because they can splatter caustic soap batter all over your kitchen (and you).
Stick blender only, friend!
MY RECOMMENDATION: Kitchenaid 2-speed stick blender
Small Kitchen Scale
Always measure soap making ingredients by WEIGHT (on a scale) and not by volume (in measuring cups). Weighing out your ingredients gives a more precise measurement than measuring by volume. And when working with lye, precision is important!
The ingredients in soap recipes are all listed by weight. You can’t use measuring cups instead, because weight measure and volume measure of oils are different. For example, 2 ounces of coconut oil by weight is NOT equal to 2 ounces of coconut oil by volume.
To get correct measurements, and create a safe bar of soap that is not lye heavy, all ingredients must be weighed.
Which means, you’ll need a scale. Small digital kitchen scales that weigh in both grams and ounces, and up to 5 lbs., are perfect. You can buy these in the kitchen gadget aisle of most big box stores, or get one online.
MY RECOMMENDATION: My Weigh KD-8000 Digital Scale
In this, you’ll dissolve the lye into the water. Lye water (also called lye solution) gets hot. As in, over 200 degrees Fahrenheit hot. So your lye water receptacle must be sturdy and heat safe.
I recommend a 2-quart sized, plastic #5 pitcher with a spout, for controlled pouring. Check the bottom of your pitcher, inside the little recycling symbol. That number should be 5. This type of plastic is very sturdy and can handle the heat of your lye solution.
Have a pitcher with no number that you’d like to use? Here’s a quick way to test it’s up to the task before you fill it with scalding lye water. Bring a pot of water to a boil. Set said pitcher down into your sink and pour the boiling water into it.
If your pitcher sags, warps, softens, or does anything other than sit there mightily, don’t use it for soap making.
Another note, don’t use a glass pitcher or container for lye water. The rapid temperature change when lye is mixed with water can shatter glass containers. Lye can also etch the glass over time, making it more likely to shatter.
Lye water + broken shards of glass = no good, my soapy friend.
Plastic totally eliminates this problem. I’ve had some of my soap making pitchers for nearly a decade and they’re still going strong.
MY RECOMMENDATION: Rubbermaid 2-Quart pitchers (2-pack)
Plastic Measuring Cups with Spouts
But didn’t I just say not to measure your ingredients with measuring cups? You’ve got an A for paying attention! You will be using these to measuring your ingredients, but not by volume.
Instead, place these measuring cups on the scale and weight out ingredients into them. The handle and pour spout makes it easy to keep things neat and tidy.
You’ll need two of these, one for measuring out your oils and one for measuring out your lye. Remember, plastic only because lye can etch glass!
MY RECOMMENDATION: Measuring cups with spouts (3-piece set)
I love these for stirring lye water solution, scraping oils out of measuring cups, and getting every last bit of soap batter out of the pot and into the mold.
Silicone spatulas are sturdy and durable, and aren’t prone to soap making wear and tear like wooden spoons are. Plus, they’re cheap.
You’ll need at least two of these, one for mixing lye solution and one for oils/soap batter. But I can easily use five or six of these during one soap making session if I’m using lots of different colors in my soap (one spatula per color). So, having a few extra silicone spatulas on hand is a good idea.
MY RECOMMENDATION: Silicone spatulas (7-piece set)
There are many different types of soap molds available, and the mold you ultimately decide on depends on what you’d like your finished bars to look like and how much you want to invest in your soap mold.
Some of my favorite options:
Silicone soap molds: These are a breeze to use. No prep, just pour your soap in and pop out when it’s done. A favorite among soap makers is this 2 lb. size loaf soap mold.
Wood soap molds: Considered the gold standard in soap molds because they hold heat well and last forever. I’ve had the same wooden soap mold for 20-plus years and it’s still as perfect as day one. Those that come with silicone inserts are super easy to use.
Silicone baking trays: These make awesome soap molds! Since they’re using for baking, they can handle the high heat of your soap batter. Silicone muffin trays come in all types of fun shapes, while the silicone loaf pans and baking sheets make lovely loaf and slab molds.
Soaper’s tip: Place these molds on a sturdy cookie sheet prior to filling. This makes it easier to move your soap and less likely to spill.
Don’t use rigid clear plastic soap molds. These are designed for melt and pour soap and can’t stand up to the heat of cold process soap.
Also, it’s nearly impossible to unmold cold process soap from rigid plastic molds, because bars are soft and sticky for several weeks after they’re made.
(P.S. If you’re looking for frugal mold options, I’ve got some ideas for you in the section below, so keep reading!)
If you’re going to add fragrance or essential oils, color, oats, herbs, or other additives to your soap (and, of course you are, because that’s part of the FUN!) you’ll also need a few random supplies to add to your soap making kit:
- Small bowls for measuring minute amounts of additives
- Sturdy spoons for scooping out solid-at-room-temperature oils (like coconut oil or palm oil)
- Ladle for removing soap from pot and pouring into mold
- A soap cutter or a large non-serrated knife for cutting your soap into bars (or get this set with soap molds and cutters)
Ways to Save Money On Your Soap Making Supplies
Getting all of the supplies you need to make soap can be a bit of an investment when you’re first starting out, especially if you’re not sure you’re going to like making soap. (But… I’m pretty sure you’ll fall in love with it!)
You don’t have to spend a ton of money in the beginning. Here are some inexpensive ways to get started making soap from scratch:
Ask friends and family if they have any of these supplies in their kitchen gathering dust. This is an especially good way to score a stick blender. People often buy a stick blender (or are gifted one) use it once or twice, and stash it in the deep recesses of a kitchen cabinet and never use it again.
They may be glad to get rid of these unused items for just a few bucks or even give it to you in exchange for a few bars of your awesome, soon-to-be-made handcrafted soap.
Hit up garage sales and thrift stores. These places are pure gold for inexpensive soap making supplies. I got my first stick blender at a thrift shop for $3. I can’t remember what I paid for my first soap pot, but I do know that I bought at a garage sale for less than $5. You can also find silicone baking trays, spoons, and spatulas.
Shop your local dollar store. All these years later, and I still get most of my soap making incidental tools at the dollar store. My local store always stocks #5 plastic pitchers, plastic measuring cups, silicone spatulas and spoons, EYE PROTECTIVE GOGGLES (Yes! Wrap-around type and everything!), skewers for doing swirl techniques, and tiny bowls perfect for measuring out fragrance or essential oils, colorant, and herbs.
You can nearly get all the supplies you need here, besides the pot, scale, and and stick blender. How’s that for one-stop shopping?
Repurpose small boxes as soap molds. Small boxes make lovely, inexpensive soap molds. So, start hoarding those old shoe boxes (or, if you’re an avid Amazon shopper like me, shipping boxes.)
Cold Process Soap Terms to Know
Ready to learn some soap making lingo? Here are a few key soap making terms that it’s important you understand, since you will regularly come across them in soap recipes and instructions.
What Is Saponification?
Remember, the chemical process of turning liquid, lye, and oils into soap is called saponification.
During saponification, the ingredients thicken and produce heat. Your soap batter will generate its own heat for several hours as it sets in the mold.
If you touch the outside of your mold several hours after pouring, you’ll notice that it’s as hot, or hotter, than when you first poured in the batter. Pretty cool.
Once saponification is complete, soap will gradually cool down and solidify. Saponification generally takes 24 hours to complete.
What Are Saponification Values (or SAP Values)?
The saponification value (also called SAP value) is the amount of lye needed, in ounces, to turn one ounce of oil into soap. Every oil has its own saponification value.
Here’s an example (hang on, friend, we’re going to do a wee bit of math):
Coconut oil has a saponification value of 0.191. That means it takes 0.191 ounces of lye to turn 1 ounce of coconut oil into soap. So, if you are using 10 ounces of coconut oil in your soap recipe you would need 1.91 ounces of lye to make soap (0.191 X 10 = 1.91).
Jojoba oil has a saponification value of 0.0695, so it takes 0.0695 ounces of lye to saponify 1 ounce of jojoba oil. For soap made with 10 ounces of jojoba oil, you would only need 0.695 ounces of lye (0.0695 X 10 = 0.695).
You can see, it takes almost three times as much lye to turn 10 ounces of coconut oil into soap than the equivalent amount of jojoba oil. Why is that?
Every oil has its own unique mix of triglycerides, so each oil needs a different amount of lye to properly covert into soap.
Knowing the saponification value of each oil allows soap makers to calculate the perfect amount of lye needed for every recipe, and avoid the lye-heavy bars that were common in old time soap.
So, how do you know the saponification value of each oil? For that, you can refer to a saponification chart—a chart that lists individual oils along with their unique saponification value.
You can also plug your oils into an online lye calculator. You enter the amount of each oil you are using and the calculator computes the amount of lye you will need. There are several free lye calculators online, but the one that I use most often is Bramble Berry Lye Calculator.
Of course, when you’re first starting out you don’t have to formulate your own soap recipe right away. Even if you’re following someone else’s recipe, knowing SAP value is important because it gives you a better understanding of how soap is made.
What Is Superfat and Lye Discount?
When you start looking deeper into saponification values of oils, you’ll notice something interesting: Different saponification charts list different SAP values for the same oil. How can that be?
The exact SAP value for any particular oil is the precise amount of lye needed to turn 1 ounce of said oil into soap. When using the exact SAP value there is no wiggle room; if there is even the slightest overage amount of lye, perhaps due to a small mismeasurement or a scale calibration that is a bit off, you will end up with lye in your finished soap bar. No one wants that!
So, most saponification value charts use a lye discount. They list slightly less lye than is required.
Some free oil remains in the finished bars, because there is less lye than is needed to turn the entire amount of oil into soap. This extra oil is the superfat.
Superfat is measured in percentages. So, soap with 7% of the total oil left as free oil in the bar, has a 7% superfat. Soap made with 10% superfat has 10% free oil.
Superfatting your soap does two things. First, the extra oil left in the bar makes your handmade soap extra moisturizing.
Secondly, and most importantly, creating your soap with a superfat gives some extra wiggle room when measuring lye, ensuring you will never end up with a lye-heavy bar even if there are slight mismeasurements.
For example, if you plan a 8% superfat for your soap, and there is a slight over-measurement of lye, you may end up with a 7% superfat soap instead. No big deal!
But, if you used the exact SAP value of your oils and there was a slight over-measurment of lye, you could end up with 1% extra lye in your finished bar. Big deal!
Circling back to why different saponification charts show different saponification values for the same oils: it depends on the lye discount, or superfat level, the particular chart is calling for.
Here’s a quick example of the SAP values of olive oil with varying superfat levels:
- 0% superfat = SAP value 0.14
- 5% superfat = SAP value 0.13
- 10% superfat = SAP value 0.12
So, depending on the superfat level of the particular SAP chart you are using, you will see slightly different SAP values for the oils.
Most SAP charts label the superfat level, or lye discount, used.
I recommend using a 6% to 7% superfat level (6% to 7% lye discount). This gives just enough free oil in the bar to be moisturizing while ensuring enough wiggle room to avoid lye heavy bars.
What Is Trace?
In every soap recipe, you’ll see a directive saying, “blend until trace.” Trace just means that the soap batter has begun to thicken. Once thickening starts, you know that saponification has begun!
There are stages to trace. The batter begins to thicken slightly, and continues to thicken until it turns into solid soap.
Some recipes call for blending to a specific stage of trace. Here’s a good reference:
- Light trace: The soap batter is a gravy or pancake batter consistency.
- Medium trace: Cake batter consistency
- Heavy trace: Pudding consistency
If the soap recipe you’re following doesn’t specify, blend until the batter starts to noticeably thicken, or medium trace.
As you gain experience you will find your own personal “sweet spot” where you like to get your soap batter before pouring. I pour my batter between medium and heavy trace. Other soap makers who do intricate, fluid swirls pour at a very light trace.
It’s also important to know that certain recipes come to trace faster than others. Soap recipes with high amounts of olive oil, for example, take a lot of blending to come to trace. Recipes with high amounts of solid oils with trace much more quickly.
Some fragrance oils can make your soap batter trace within seconds; this is called acceleration. So, if you see a fragrance oil that says “accelerates trace,” you’ll want to blend to just light trace and work quickly to get it into the mold. Other ingredients that can make your soap trace faster are clays and oatmeal.
Can You Substitute Oils in Cold Process Soap?
Say you’ve found a soap recipe you’re excited to try, but it calls for sunflower oil which you don’t have on hand. Is it OK to substitute another oil?
Remember, each oil has its own saponification value, which determines the specific amount of lye needed in each recipe. If you simply swap oils, you can easily end up with the incorrect amount of lye.
You can’t substitute oils in any cold process soap recipe unless you also recalculate the amount of lye needed.
Oils in every soap recipe are chosen for a specific reason, to make a bar that is cleansing with good lather, but still moisturizing and conditioning to the skin. Substituting one oil for another can leave you with a bar that isn’t balanced.
When you are a beginner, I highly recommend following recipes exactly and avoiding substitutions.
Once you have more experience, you can experiment with substituting oils. Until then, either buy the oils you need, or choose a recipe that works with the ingredients you have on hand.
What Is Cure?
Beginning soap makers typically have lots of questions about cure, but honestly curing your soap is super simple. Here’s what you need to know:
How Do You Cure Soap?
To cure soap, simply set the bars on brown paper or butcher paper and place in an out of the way spot like a closet or shelf. Turn the bars once every week or so to expose all sides to air.
You do not need to wear gloves to turn your soap at this point. It’s safe to touch with bare fingers.
How Long Does It Take to Cure Soap?
Most soap takes 30 days to cure. But certain soap recipes, like those that contain lots of olive oil or goat milk, for example, can take 60 days or longer. If your soap still feels soft, squishy, or sticky after 30 days, let it set for two more weeks and try it again.
Why Does Soap Need to Cure?
When you unmold your soap it will be soft and sticky, similar to a soft cheese. The curing process allows the excess water within the bar to evaporate away, creating hard bars that are ready to use.
Can You Make Soap Cure Faster?
Unfortunately, no. Although some soap makers claim you can speed cure by placing a fan to blow over your bars, or putting the soap in the oven on low, helps speed curing research has shown otherwise. Time is the only way to fully cure soap.
Can I Use Soap Without Curing?
Technically, soap is safe to use before cure. Saponification is complete after about 24 hours, which means the soap is no longer caustic.
It won’t be very pleasant to use before curing, though, because the bar will be super soft and slimy, won’t lather well, and will melt away really fast. A good cure improves your soap immensely.
Finding Good Cold Process Soap Recipes
One of the absolute most important thing you can do when you are a beginning soap maker: only use trusted, tried-and-true cold process soap recipes.
If the recipe you’re using is a stinker, here are some of the problems you can run into:
- Ratios of oils are off, creating a bar that is either too soft, too drying, doesn’t lather well, or melts away too quickly.
- Too little lye in the recipe, leaving you with mushy, oily goop rather than soap.
- Too much lye in the recipe, which is the most worrisome of the bunch because it leaves you with lye in your finished soap bar. This can cause major skin irritation and/or eye injury.
But when you’re first starting out you don’t have the experience to know, just by looking at the recipe, whether it’s a good one or not. So what’s a beginning soap maker to do?
If you’re choosing cold process soap recipes off the internet, I highly suggest running it through a lye calculator first.
You just enter in the amount of each specific oil in the recipe. The calculator will determine the amount of lye needed for that recipe.
The amount of lye the calculator suggests needn’t be exactly the amount called for in the recipe, but it should be very close.
Lye measurements may be a bit different depending on the superfat of the recipe compared to how the calculator computes.
So, if the recipe calls for 4.8 oz. of lye, and the calculator figures 5 oz. of lye, you’re in the right ballpark. If there is just a few tenths of a difference between the two, your recipe is OK as-is.
But, if the recipe calls for 7 oz. of lye and the calculator says to use 5 oz., that’s a considerable difference! If this is the case, follow the lye calculator.
Typos or miscalculations happen, even in recipes from trusted sites. This is why I always recommend doing a double-check of lye amounts with any recipe
MY RECOMMENDATION: Bramble Berry’s Online Lye Calculator
Basic Cold Process Soap Making Instructions
You made it through all the soap making basics… so are you ready to get your hands dirty (or, uhh, clean?) and actually make some soap?
Sign up to get the free Step-By-Step Cold Process Soap Making Cheat Sheet + Lye Safety Checklist. This printable cheat sheet walks you through the entire soap making process, from start to finish. It also includes a checklist to ensure you never forget a lye safety step, so you can soap safely.
This cheat sheet is typically reserved for students in my How To Make Soap From Scratch course, but I’m sharing it here because I know it will be super helpful to you as a brand new soap maker.
Enter your info in the form below, and I’ll send the checklist + cheat sheet to your inbox right now.
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Get Personalized Soap Making Instruction
I want you to absolutely love making soap, and become a confident and successful soap maker. I’m always here to help you out…
You can post any questions you have either in the comments section below this post, or drop me a note on the Farm Girl Soap Co Facebook page.
Also, remember to sign up for the Step-By-Step Cold Process Soap Making Cheat Sheet + Lye Safety Checklist above. (You’ll also be subscribed to my weekly newsletter, where I share new DIY skin care recipes and mini classes.)
If you’re ready to dive into soap making and would like some step-by-step instruction, check out the online course How To Make Soap From Scratch (Even If You’re Crazy Scared of Lye) at my Farm Girl Soap Co Schoolhouse.
Easy video tutorials walk you through the entire process, from beginning to end. It’s like having me right next to you as you make your first batches of soap.
(Want to see what it’s all about? Take a lesson for free; you’ll learn all about how to cure your soap.)