How to Make Cold Process Soap

Since making soap is a chemical reaction, you need to take the proper safety precautions to protect yourself from the corrosive substances and high heat.

Handling Sodium Hydroxide (Lye)

To make soap, you’ll need to combine two chemically opposite forces. On one hand, you have your fatty acids, in the form of your oils. On the other hand, you have your corrosive alkaline solution, in the form of sodium hydroxide (lye), which forms your base.

You must take proper safety precautions when handling sodium hydroxide, in both its solid state and when mixed with water. If the sodium hydroxide comes in contact with organic matter, your skin and eyes for instance, you will experience a chemical burn. If sodium hydroxide comes in contact with your eyes, it could cause permanent blindness. Also, lye and fresh soap can be fatal if swallowed.

Now, take a deep breath…inhale…exhale. The nervousness you may be feeling about handling lye for the first time can be overwhelming. I was terrified my first time, but I’m glad I went through with it, because now I have the ability to produce as much useful and beautiful soap as I want. I’ve since made hundreds of pounds of soap, and I still always wear my safety gear, not because I’m afraid, but because there’s no reason to take an unnecessary risk.

With the right amount of respect for sodium hydroxide, the right protective gear and mindfulness, you too can handle making soap.

Required Safety Gear

1. You need to wear gloves. My favorite gloves are dishwashing gloves because they’re thick and because they reach up higher than wrist length gloves. Dishwashing gloves will also help because, well, you’ll need to wash the soaping dishes while wearing gloves when you’re done making soap.
2. Even if you wear glasses, protect your eyes with goggles. You don’t want lye or soap to be able to splash on your face and get in your eyes.
3. Use a respirator over your mouth. When mixing your lye water or handling fine powders such as charcoal and mica, use a respirator so you don’t get any particles or fumes in your lungs.
4. Wear long sleeves, pants and closed toed shoes. For your clothes, loose and flowy is better than tight. The raw soap batter may discolor your clothes if you get it on yourself, so use an apron if you have one, or wear clothes you’re not afraid of messing up.

In Case of Emergency

If you happen to get lye, the lye solution or fresh soap on yourself, you need to continuously flush the area with water for 10-15 minutes. For this reason, when making soap, do so in a location with easy access to a sink in case of emergency.

If you get get lye, the lye solution or fresh soap in your eyes, remove your contact lenses if you’re wearing any, and rinse your eyes with water for 10-15 minutes.

In both cases, seek urgent medical attention.

Lye, the lye solution and fresh soap can be fatal if swallowed.

If you do swallow lye, the lye solution or fresh soap, do not induce vomiting. Drink copious amounts of regular tap water to dillute it and call 911 immediately. Then call the Poison Control Center.

Make Soap in a Well Ventilated Area

Dissolving your lye in water is an exothermic reaction that gets very hot and produces dangerous fumes. To reduce the risk of breathing in the fumes, mix your lye water in a well ventilated area, such as near open windows or doors, or outside, and use a respirator. I make soap in my garage and open the big garage door to let in a breeze.

Be careful not to breathe in the fumes. Stand as far away from the solution as possible when you’re mixing.

Additional Precautions

Keep your lye and lye solution in a location where children, pets and unsuspecting family members will not get to it. Lock it up if you can. Label your solution so others know to stay away.

When making soap, never use aluminum containers. Aluminum and lye react to produce a poisonous gas. Use only glass, stainless steel, silicone, or heat safe plastic, for your utensils and containers.

Always add your lye to your water a little at a time. If you add your water to your lye you could experience a violent reaction.

Things Will Get Hot

Adding sodium hydroxide to water gets VERY hot within just a few seconds.

Your water will go from being room temperature to being between 150º-190º Fahrenheit by the time you finish adding your lye.

When mixing your lye water, use a heat safe container, such as glass or heat-resistant plastic. Mason jars are designed to withstand high heat so they are a great and inexpensive option. Pyrex containers are also ideal.

Be careful when touching and moving the container with your lye water. The container will be hot, especially the sides and the bottom, where the lye water comes in contact with the vessel.

What You’ll Need to Make Soap

To make soap, you’ll need to invest in soaping equipment and some special ingredients that might be hard to find in your neighborhood.

Equipment

Earlier we covered the safety equipment you should be using:

• Goggles
• Gloves
• Respirator/Face Mask

Here is the rest of the equipment you’ll need:

• Scale
• Temperature Gun
• Stick Blender
• Small Container for Lye Water – use glass, heat-resistant plastic or stainless steel
• Large Container for Soap Mixture – use glass, heat-resistant plastic or stainless steel
• Soap Mold – silicone molds do not need to be lined
• Parchment Paper and Tape to line Mold (if not using silicone)
• Small Spatula or Spoon – use silicone, heat-resistant plastic or stainless steel
• Large Spatula – use silicone or heat-resistant plastic
• Whisk – use silicone or heat-resistant plastic
• Knife or Other Cutting Device

For your containers and utensils, do not use the same ones you use for cooking. Once you use them, keep them separate from your cooking equipment so you don’t get confused.

I’ve tried using a hand mixer with whisks, like the kind you use for baking, to mix my soap. Getting my soap to trace took forever, so I recommend using a stick blender since it takes less time.

You can find inexpensive containers and utensils at your local thrift store. That’s where I found all of mine.

One of my customers told me that when she lived in Cuba, not only did she make her own soap, but she grew her own ingredients! Lucky for you and me, we can buy our supplies online; although, it is fun to harvest what you can from your surroundings.

Recipe Ingredients

We’re going to be making a very basic soap recipe. These 3 ingredients are absolutely necessary:

• 55g of Sodium Hydroxide Lye
• 102g of Distilled Water
• 387g of Coconut Oil

There’s sodium hydroxide lye and potassium hydroxide lye. These are NOT the same. Make sure you get sodium hydroxide.

You can use organic or regular coconut oil for this recipe, like the kind you find at the supermarket. You can NOT substitute one oil for another so don’t use olive oil or canola oil instead.

The oil will be equivalent to about 14 fl. oz. of coconut oil, which is a larger jar of coconut oil.

Every oil requires a different amount of lye in order to produce soap that is safe to use. There are soap recipes that use a different combination of oils, but the amount of lye has been adjusted in order to saponify the oils. So if you want to use different oils, use a different recipe.

The three basic ingredients above are all you need to produce the chemical reaction to make soap. The amounts must be exact.

When it comes to everything else, you get to choose the additives, colorants and decorative botanicals. You have more flexibility when it comes to adding other ingredients.

I enjoy harvesting my botanicals from the neighborhood when I’m walking Dino. I pick up eucalyptus branches on windy days, pluck lavender blooms and collect fallen rose petals to use to decorate my soap.

If you’re going to be using a fragrance oil, be sure to add the correct amount of fragrance that the fragrance manufacturer recommends. I buy my fragrance oils from Brambleberry, so I use their fragrance oil calculator to determine a safe amount.

Same if you’re going to be using essential oils. You’ll need to do your research on how that specific essential oil behaves in soap. Not all essential oils are appropriate for soap, either because the delicate compounds don’t hold up well in the soapmaking process, or because they’re not safe to use in the huge quantities required for soap. The essential oils could also react with the lye, so be careful.

Where to Purchase Soap Supplies

You can find soapmaking supplies at the following places:

• Brambleberry
• Mountain Rose Herbs
• Bulk Apothecary
• Arizona Soap Supply

None of these are affiliate links. They’re all suppliers I personally use and recommend.

What Goes Into Creating a Soap Recipe?

I have already created a ready-to-use recipe for you. This section is made for you to understand what went into making the recipe.

Earlier I mentioned how critical the right ratio of lye to oil is. If you have too much oil and not enough lye, your bar will end up mushy and be very oily. If you don’t have enough oil and have too much lye, then your finished soap will have free floating lye which will harm your skin.

We need to get this balance just right with our soap recipe and in order to do so there are two things you need to learn about, saponification values and superfatting.

Saponification Values

Each oil has a different fat profile. The saponification value or SAP value is a “measure of the average molecular weight (or chain length) of all the fatty acids present” in the oil and will help us determine how much lye is appropriate.

Take a look at the saponification value for some common soap making oils. Notice the variance.

Oil / SAP

Avocado Oil / 0.133

Coconut Oil / 0.178

Castor Oil / 0.135

Olive Oil / 0.134

Sweet Almond Oil / 0.136

See more saponification values.

This is why you can’t substitute one oil for another.

Calculating the right amount of lye for your soap becomes more complex as you add additional oils to your recipe because each my be multiplied by it’s SAP value in order to determine what the ultimate amount of lye will be. Luckily, there are lye calculators that do this work for you so you don’t have to do the math manually like I do below.

Whenever you get a soap recipe online, run it through a lye calculator just to be sure the person who created the recipe did not make a mistake. I’ve found a couple of recipes that I wanted to use that were lye heavy. When this happens, do not use the recipe and notify the recipe maker.

For this recipe, we’re only using one oil for the sake of simplicity.

387g of coconut oil x 0.178 saponification value for coconut oil = 68.86 g of lye 

(we still need to add our superfat so this isn’t the final amount of lye)

Superfatting

Once you have enough oil to counteract the lye, the leftover oil remains in the bar to coat your skin in a thin layer of nourishing oil. This skin-loving leftover oil is referred to as the superfat.

Typically, you’ll see recipes that have a 2-10% superfat. The higher the superfat, the more extra oil that remains in bar.

The 100% coconut oil recipe I shared with you has an even higher superfat which is closer to 20%. This is still an appropriate superfat for this recipe because coconut oil has amazing cleansing properties. It not only leaves your skin squeaky clean, but it also washes away your skin’s natural oils. The extra high superfat counteracts this so your skin doesn’t feel dry.

An extra high superfat also has the added advantage of giving us a wider margin for error. The exact saponification value of each batch of oil is slightly different depending on where it originates. Plus, your scale may not be calibrated correctly or you may drop in a little extra lye by mistake and not notice. The extra high superfat gives you a cushion of extra oil to counteract mistakes (within a certain range).

If you’re using a 14 fl oz jar of coconut oil, you may not have the exact 387 g of coconut oil that the recipe calls for. This is because fluid ounces are not measured by weight, so you may be a several grams under 387 g. As long as you have at least 365 g, you’ll still have a 15% superfat if you use 55g of lye, so the recipe will still produce a safe and nourishing bar of soap.

To calculate the superfat, you’ll convert your superfat to a decimal and subtract it from one. Then you’ll multiply that number by the amount of lye we got in the previous section.

(1-.20 superfat) x 68.86 g of lye = 55g of lye

Mix Your Lye Water

Use your scale to weigh your distilled water and lye separately. Add the lye to the water a little at a time while mixing until the lye dissolves completely, being careful not to splash. I add my lye in about 1/3 at a time and don’t add more until it is dissolved.

Set aside in a protected location (label it or lock it up so pets, children and other people won’t get to it) to cool for about one hour, until the temperature reads between 100°- 110° F.

Prepare Your Oils

Use your scale to weigh the coconut oil in a heat proof container that will be big enough to add your lye water to. Melt your coconut oil in the microwave in short 10 second bursts until the temperature reads between 100°- 110° F. Stir the coconut oil until the oil is completely melted.

You want to prepare the coconut oil right before you’re ready to soap, when your lye water is almost cool. If you melt your oils right after preparing your lye water, then they will cool and be too cold by the time your lye water is ready an hour later.

Mix Your Lye and Oils

Insert the stick blender into the oil at an angle and tap it on the bottom while it is still tilted to release any bubbles that may be trapped in the head of the stick blender. Carefully pour your lye water into your oil along the shaft of the stick blender so you don’t produce any bubbles.

Using short pulses, mix your lye and oil until you reach a thin trace. You want to pulse for a few seconds, then pause, make a couple circles in the container, and then pulse again. If you only pulse with your stick blender, the bottom of your soap mixture will be overmixed and thick while the top will still be oily and thin. Mixing in between pulses allows you to incorporate the whole mixture together so it has an even texture.

Once you’ve reached a thin trace you’re ready to add your other ingredients. You can tell if you reach trace by dribbling trails in the top of the soap. If you can see lines as the soap starts to pile on itself, you’ve reached trace. You can see this in the video.

When you can see faint trails, add your fragrance, colorants and other additives. Use a whisk to incorporate everything, being careful not to overmix. I sometimes give it a couple extra pulses with my stick blender if I’m having trouble blending everything by hand, and if my soap batter is still fairly thin. When you get to a noticeable trace when you can clearly see trails forming, stop mixing.

Some soap recipes recommend adding your fragrance oil and other additives to your melted oils before you add your lye water. While this is a good idea if you tend to forget to add your fragrance, it could cause the soap to trace too fast. This also depends on the kind of oils and other ingredients you’re using.

For your first few times, I recommend adding your additional ingredients once you’ve reached a thin trace and then mixing in your other ingredients by hand. That will reproduce the most consistently successful results when you’re first starting out.

Pour Your Soap Mixture Into the Mold

When your soap mix is ready, carefully pour it into the mold you do not need to insulate your soap.

Decorating my soap bars is my favorite part. Each batch comes out unique and is a new opportunity to experiment with different designs.

You can texture your bars with a spoon, make lines with a fork, or use a skewer to make swirls. You can top your soap with dried botanicals that you’ve harvested or soap shavings from previous batches.

The options are endless.

Cleaning Up

The best time to clean up is immediately after you’ve poured and decorated your soap. At this time, you’re still wearing your long sleeves and gloves, so you can touch the raw soap without harming your skin.

The soap is also still soft so you can wipe down your soaping containers with a paper towel and then give it a quick rinse. Don’t wipe down your lye water container, just rinse it.

Use a separate dish brush or sponge to wash your soap containers and equipment. Don’t use the same one you use to wash your food dishes.

When you’re done washing up, make sure you flush your sink with lots of water so no lye is left behind.

Then store your containers and equipment once they’re finished drying in a place separate from your food containers. They’ll be clean and ready for the next time you’re ready to make soap.

Unmolding and Cutting Your Soap

Check on your soap every few hours. You’ll want to cut it when it feels like refrigerated butter. It should feel firm and dense. I find the sweet spot is after about 6-9 hours, but this will depend on the weather. I suggest making your soap in the morning on a day you’ll be at home so you can monitor it.

Coconut oil soap has to be cut within about 12 hours of pouring, otherwise it will be too hard to cut. If you wait too long, your soap will be hard as a rock and will crumble when you cut it.

Be sure to wear gloves when cutting your soap.

Once your soap has been unmolded and cut, then set them on a tray and place them in an open area out of direct sunlight. Your soap now has to cure for 4-6 weeks. Waiting is hard, I know, but you’ll be rewarded with a milder bar of soap that lasts much longer once the excess water in the soap has had time to evaporate.

Plus you’ll be able to enjoy them visually while they’re curing and they’ll release their fragrance throughout the room they’re curing in.

You’ll notice that as your bars cure they will shrink, so if you’re wrapping labels around your soap, wait as long as you can to label them. Otherwise the labels will fit loosely as time goes on.

Once your soap has cured, store them in a cool dry place. A clothes drawer or linen closet is the best, so they can perfume your clothes. Use within 12-18 months. All natural oils eventually go rancid. When this happens, your soap bars will develop what is known as DOS or dreaded orange spots. This means the oil has spoiled.

If this happens your bars are still technically safe to use, they’ll just be uglier and stinkier so use them up! And encourage the people you give them to, to use up the soap you made for them so you can make more.