The Ultimate Beginners Guide to Cold Process Soap Making

Ever wanted to make your own soap from scratch but not sure where to start? Well look no further! Here’s our ultimate beginners guide to cold process soap making, which covers everything you need to know to get started! Enjoy! :)

First off, what is cold process soap making and how does it differ to other ways of making soap?

This type of soap making involves mixing non volatile animal or vegetable fats/oils with an alkali (i.e. Sodium Hydroxide/Lye/NaOH) to saponify the oils - the oils will change during this saponification reaction and ultimately form soap. Note, after your bars are cured, there is no lye left in your product, only saponified oil. You can also make soap via either hot process or Melt and Pour. Hot process is where you’re actively cooking the soap rather than letting it saponify on its own. In Melt and Pour, you use pre-made soap bases, melt them and then pour your mixtures into a soap mold - no lye required on your end (although it would have been used to make the initial soap base). The big win for cold process is that you have the most control over the ingredients in your soap which will control the look, shelf life and feel of your end product. However, this method is a bit trickier and requires a bit more knowledge about the ingredients you use and how they interact during the process compared to melt and pour. For example, different oils will give you different effects for your bar, certain fragrance and essential oils can react with your mixture at different concentrations, and some color additives either don’t survive the process or turn a different color. In addition, this process requires a 4-6 week curing time. With all of that said, I personally think the benefits far outweigh the challenges in cold process soap making!

Above is the chemical reaction that takes place when you mix oils (triglycerides) with lye (NaOH). As you can see, after the reaction, you end up with soap and glycerin (glycerol) - glycerin is a humectant and a nice moisturizing ingredient that’s often added to other cosmetic products for it’s effects, but conveniently, it’s naturally found in cold process soap making. Cold process soap is as a result also sometimes called glycerin soap. As you can see, there’s no lye left after the saponification reaction takes place.

Fun fact about glycerin in soap making, in the late 1800’s Alfred Nobel discovered the significance of nitroglycerin as an explosive, leading to the invention of practical ways to extract glycerin from soap. The demand for glycerin turned soap manufacturing into a big money business - until the 1940’s, most glycerin was made as a soap manufacturing by-product. This method remained popular until a method to create glycerin from synthetic ingredients, like propylene (from petroleum) was developed. Today, many bigger soap manufacturers remove glycerin from their soaps to use in other products with a higher price tag, like creams. Unfortunately, when glycerin is removed from soaps, they can become very drying to your skin.

Lye Safety

Cold process soap making doesn’t have to feel scary - I hear frequently from folks at our workshops that they’re afraid to use lye. At the end of the day, being aware of the risks and how to mitigate them will make the whole process a lot less intimidating. At the end of the day, if you want to make soap, this ingredient is absolutely essential to saponify your oils and give you a lovely homemade soap.



Lye is an inorganic alkali ingredient that’s extremely corrosive. It’s frequently found in products like drain cleaners due to this effect. This ingredient is very caustic and can burn your skin. With that said, it can be perfectly safe as long as you handle it properly. Lye is available in a variety of forms, such as powder, pellets and flakes. To make your soap, lye is introduced into water (or other aqueous solutions when you get more advanced), dissolving into a lye solution. Mixing water with lye will create a lot of heat and the mixture creates fumes which you should not be inhaling.

Here are a few safety tips to be aware of when you make cold process soap:

  1. When you’re making soap, wear eye goggles, gloves, long sleeves and long pants. This will help protect your skin if you spill any of your soap mixtures onto your skin. For fumes, many soap makers like to wear ventilation masks. Wear this during the whole soap making process.
  2. When you make your lye solution, make sure the place you're making it in has good ventilation.
  3. Always add lye to water and never water to lye. The opposite can result in a bit of an eruption, which you definitely don’t want.
  4. Store your Lye in a clearly labeled container to ensure no one touches it and never store within the reach of children. Also, make sure the lye is in a closed container in a cool and dark place.
  5. If you get Lye on your skin, remove any clothes that were also exposed and flush immediately with lots of water for at least 15 minutes. Do the same if you get it into your eyes. For both cases, if you get burnt, seek medical attention. If you inhale lye, move to fresh air.
  6. Make sure the containers you use to make your lye solution are sturdy, a heat-tolerant plastic or glass. Metal containers are not recommended for they can react with the lye solution and be quite dangerous.
  7. Once you pour your lye solution into the oils, the saponification process begins. As it develops, the lye solution becomes less dangerous. With that said, it can still be extremely irritating to your skin. If your soap batter touches your skin, it may take several minutes to start tingling and burning - be sure to thoroughly wash off as soon as you notice if this happens. Leave your gloves on as you wash your dishes and use grease-cutting soaps.

Note, I’ve never experienced a serious lye burn myself as it’s pretty easy to avoid with the right precautions. I have gotten the batter on my skin many times but was able to wash it off quickly to avoid any serious harm.  

Where can you buy Lye? It’s very rare to find this ingredient in stores but pretty easy to find online. I like to purchase my lye from Voyageur Soap and Candle Making Supplies. Wherever you decide to get your lye from, be sure that it’s 100% sodium hydroxide and make sure the vendor is a reputable source. Buying in bulk is a great way to save money on your lye especially if you have a few other soapers to carefully share the ingredient with. To make sure that your lye will work, I recommend using it within a year of purchase and storing it in a tightly sealed and dry place. Note, lye attracts moisture which will make it a lot less effective.

Definitions For Key Soap Making Terms

Trace: After you mix your lye solution into your oils and start mixing, your mixture will eventually turn into a thicker, pudding-like consistency. This is trace. Trace is referred to as light, medium or heavy depending on the thickness of the mixture.

Here's an example of a medium trace by the She Holds Dearly blog.


Gel Phase: After you get your soap batter into your mold, the saponification process can cause the soap to heat up - this is your gel phase. This can intensify the colors in your soap and give your soap a nicer end look, ultimately this is a good thing for soap making. With that said, if your soap doesn't go through the gel phase, it doesn't take away from your soap. In fact, many soap makers take steps to prevent this phase. The warmest part of the soap will be the center, the most insulated part where gel phase begins. If you notice that the center of your soap is darker than the exterior (like a dark circle), your soap only went through a partial gel phase. Insulating your soap after molding will help achieve a complete get phase. In contrast, cooling the soap (e.g. in the fridge or freezer after you mold) will prevent the gel phase from happening. Whether or not you want a gel phase is completely up to you.

Here's a great visual by reMeld190 of what a partial gel phase turns into.


Curing: This is where extra moisture from your soaps will evaporate, leaving them harder and more long-lasting. If you use your bars too early, your soap will be slimier, softer and harsher (there still may be a bit of lye left over and the pH will be quite high). A 4 to 6-week curing time for you soaps will give you the gentlest, longest lasting and hardest bar from your mixture.

Look at all those soaps! Here's the curing racks for Soap By The Loaf, one impressively industrious soap maker!

Soda Ash: this is a salt that can develop on the surface of your bars as they cure (note, not actually Soda Ash, that's just what we soap makers like to call it), appearing like a chalky white precipitate. It’s not harmful, it just doesn’t look very good. You can cover your bars as they cure or spray with Isopropyl Alcohol to prevent soda ash from occurring. I personally like to do a water subtraction (somewhere around 10%) from my lye mixture to prevent soda ash, but this is a bit more advanced as your soap batter will trace faster and you’ll therefore have to work a lot faster. If you end up with a bit of soda ash on your bars, you can take a damp cloth after they've cured and do a good job removing it from your beautiful soaps. If you haven't done any swirls or other designs, you can also shave the soda ash away carefully. 

An example of soda ash, the white residue on the top of the bars, by Angela Palmer's Farm Girl Soap.

Lye Calculator: this tool makes soap making super easy compared to the good ol’ days when you had to calculate all the percentages of your ingredients yourself. This calculator determines how much water and lye and oils, include fragrance or essential oils in a good calculator, to include in your mixtures. Enter in the percentages of oils, and which types, you’d like to use, make sure they add up to 100% and click calculate. You can also adjust the recipe with end pounds of your mixture. Knowing how much weight fits into your molds takes a bit of experimentation but soap molds will often give you suggestions. Soap calculators will often give you estimations of the feel of your bar as well. Every oil will give your soap different effects for your end product. Learning which oils work well for you and which concentrations you prefer will take a bit of experimentation. This is my personal favorite soap calculator. In this calculator, to see your final recipe, click on the view or print recipe after you’ve calculated your recipe.


What kind of equipment do you need to get started?

Aside from of the equipment I recommended in the safety suggestions (heat tolerant and non-reactive containers, gloves, goggles, long sleeve shirt and long pants, etc), there are a couple of tools you’ll need to make soap.

  1. Stick blender: while you can hand stir your soap, this can take hours. A stick blender is an easy way to quickly emulsify your lye and oils to get the saponification reaction going.
  2. Scale: accuracy is key when your making soap, if you're off by even a couple of grams for an ingredient, this can completely ruin your end product depending on the ingredient. Kitchen scales are a nice start, but it may be worthwhile investing in a better digital scale with a higher accuracy and weight allowance as you become a more experienced soaper.
  3. Soap mold: lots of options here but the most common is wood, plastic (old clean Tupperware or yogurt containers can work well) or silicone (by far the easiest type of mold to use because of its flexibility - this makes unmolding very easy). If you use wood, be sure to line the mold. Glass would be safe, but extremely difficult to unmold. Metals aren’t the best idea because the potential for lye to react with them. Be sure to wait until your soap is completely hard (about 24 hours) before you try unmolding.
  4. Rubber spatula: to get all the soap mixture into your soap mold.


Here's one of my favorite soap molds! Not as big as some of the other professional soap molds (usually big boxes where you can make hundreds of uniform rectangle bars), but because the bars lay flat and the tops are open, I can still hand design and mold each bar! The drawback for this specific mold is that I can only make 45 bars at a time - which means, as a soaper that sells soaps, each bar takes significantly more time than if I had one of those large box molds.... but then again, my soaps wouldn't be so pretty <3. I like to get my soap molds and cutters (the thing next to the mold) from SoapEquipment :).


Getting your soap on!

I think the best way to learn how to make soap is to actually give it a try. Here’s a simple recipe to get you started. As you go through the recipe, try following along with the Lye Calculator. Doing this will make it easier for you to experiment with different ingredients the next time.

Step 0: Determine which and how much of your ingredients to use. Head on over to this soap calculator to figure that out. You can see that you the calculator is automatically set to making soap with 1 pound of oils, which is a great amount to start with. In the scroller with all of your oils, add in Olive Oil, Coconut Oil (92 degrees), Cocoa Butter and Castor Oil, which will pop up to the recipe oil list. Note, you’ll have to click the ‘add’ button for each oil. In recipe oil list, put your olive oil at 60%, coconut oil at 25%, castor oil at 10% and cocoa butter at 5% and then click calculate recipe. Next, click view or print recipe. This will bring up a new screen that describes some of the characteristics of your soap and gives you your soap recipe.

Here’s what we got from those calculations for the ingredient amounts:

Lye Solution

  • 172.36 grams of water
  • 63.28 grams of Lye


  • 272.16 grams of olive oil
  • 113.4 grams of coconut oil
  • 45.36 grams of castor oil
  • 22.68 grams of cocoa butter

    This recipe will give you a nice cleansing bar that’s decently hard and has quite bubbly (look at the soap bar quality in the calculator recipe to see how I came up with this).

    Notes about the ingredients pertaining to soap making:

    Olive Oil: gives you a more conditioning bar but when used alone can result in a softer bar with a poor cleansing effect and hardly any bubbles. You can achieve a harder bar with pure olive oil, the cure time will just be quite a bit longer. I personally always like to add other ingredients to make the bar harder (which will mean more long-lasting), more bubbly and more cleansing.

    Coconut Oil: has a very cleansing effect in soap and also produces a harder soap with more bubbles. I like to keep coconut oil under 30% since it is very cleansing and can be quite drying to your skin as a result. For more sensitive or dry skin types, I would consider dropping the coconut oil content down to about 10%. Note, I personally always like to have at least a bit of coconut oil in my soap mixtures because I want my soaps to have at least a bit of a cleansing effect, and coconut oil does a great job achieving that effect.

    Castor Oil: quite conditioning and does a good job stabilizing your bubbles, ultimately giving you a nice fluffy lather. I personally always like to use castor oil in my soap. I recommend keeping the percentage of castor oil down to under 10%. If you go above 15% you may end up with a slimy, sticky and not as long lasting of a bar.

    Cocoa Butter: quite conditioning and does a great job producing a harder bar. This effect is quite useful, especially when you're using a lot of an ingredient that creates softer bars, like olive oil. I recommend using this ingredient at a percentage under 10%. Any higher can lead to a very hard but brittle bar of soap. Alternatively, you can use palm oil here. If you use palm oil, I suggest making sure you're getting palm oil that’s been certified by the Round Table on Responsible Palm Oil (RSPO) as sustainable.

    Now let's get started on the soap making!

    Step 1: Get your safety gear on and make sure no kids or pets are around you. Measure out your lye and water amounts with your scale in separate containers. Slowly and carefully add the lye to the water, stirring until the water clears up again. Set aside. Be sure not to breathe in the lye fumes.

    Step 2: Measure out and combine all of your oils. You’ll have to melt down your cocoa butter and coconut oil before you add them to the rest of your oils.

    Step 3: After your oils and lye solution has cooled down below about 55 degrees Celsius, both ingredients ideally will be at similar temperatures, carefully and slowly pour the lye solution into your oils.

    Step 4: Pulse your stick blender to mix the lye solution with the oils and then turn the blender on to blend until you reach a trace. Be sure to have your blender fully submerged before turning it on to keep the mixture in the bowl.

    Step 5: After you’ve reached trace, this would be the time to add any fragrance or essential oils or color, starting with the color if you're adding these ingredients in. If you decide to add fragrance or essential oils, flip back to your recipe from the lye calculator. As you can see, you can add 14.18 grams of either of these ingredients. This is a little simplified but it’s a good start. If you added in any of these ingredients, mix them well with the stick blender before pouring your whole mixture into your soap mold.

    Step 6: Allow for a day or two to go by before you unmold your soap - it should be nice and hard when it’s ready to unmold. Cut your soaps as you like and let them cure for 4-6 weeks.


    There’s so much more to learn to learn about soap making. For example, there’s lots of techniques to learn to make shapes and swirls in your bars, lots of added ingredients other than oils to really amp up your recipes, and lots to learn about the oils you're using and how they will impact your end formula. As a result, I find the whole process extremely fulfilling and very interesting. As a soap maker, refining your craft is an ongoing process that really never stops. But with that said, that’s it for this post! If you have any questions, queries, conundrums, or concerns, leave them below, on any of our social media channels or feel free to shoot us an email!