In this post, you will find a detailed step-by-step tutorial that will show you how to make cold process soap, a process of making handmade soap that does not require heating (just what is necessary to melt solid oils and butters). In the end, you will get 100% natural soaps, beautiful, very moisturizing and soft and with a professional look.
In addition to this article, you can watch the tutorial video with step-by-step instructions:
Every recipe in this blog will also have its own recipe video, but this is a complete and detailed tutorial, where you can learn all details, special tips and hopefully clear all your doubts.
Transforming the ingredients into natural soap
The cold process method is the most common way to make soap from scratch. The cold process, as the name implies, refers to the temperatures used in mixing the ingredients. It is simpler than the hot process method, which involves a number of different operations, and constant heating.
It is easy enough for anyone to try and you can easily make soap in the kitchen using this process. Although there is usually some uncertainty in the first attempt, in the second you’ll get the hang of it. Soap making involves many ingredients and steps, and some accuracy, so it is very important to keep everything organized.
These step-by-step instructions for making handmade soap presented in this session are generic and, apart from some details, serve to follow any type of soap making recipe.
Step 1: Gather the ingredients and equipment
It is important to have everything prepared and organized before you start preparing the soap batter. This includes measuring ingredients, preparing workstations and organizing equipment. Because the time factor is critical, it is not advisable in the middle of the recipe to pick up any missing ingredients or necessary equipment.
It is also not good practice to measure ingredients in a hurry, it leads to measurement errors and can compromise the quality of the final soap, for example, adding too much lye can make the soap irritating to the skin.
Take the time to read and understand all the steps in this tutorial, as well as each recipe. Then, prepare everything you will need for the recipe. Never failing this important preparation step is halfway to a smooth soap making experience.
Step 2: Measure all ingredients
In order to reduce the amount of ingredients and utensils to be handled at the same time, I usually anticipate some steps, carry them out separately before proceeding to making soap:
1 – Measure the essencial oils first, with measuring spoons (in ml) or with a digital scale (in mg). I usually make a very rough approximation from mg of the recipe to ml, which usually results in less essential oils than the recipe calls for. However, recipes usually aim for maximum fragrance, so you don’t need to add the entire amount. And my soaps usually smell the same.
In this step, I usually add the antioxidant extract, in this case, grapefruit seed extract (GSE).
In order not to spill anything, you can add everything to the bottle with a dropper pipette, or use a wide-mouthed bottle. This time, I put the essential oils and the extract in a small bottle.
2 – Then, measure the amounts of dye, again, with the measuring spoons (in ml). In these photos, I used turmeric and red iron oxide as dyes 🙂
I put the mixture in a small cup.
3 – Before starting, I weigh the quantities of oils and butters, in water and caustic soda with a scale. Being an important step, it requires some attention:
3.1 – Place the bowl where the oils will be heated on the scale and set the scale to zero (usually the “tare” button). Then the oils are weighed one by one, taking care to “reset” the balance for each oil.
After these preparations, we will have to organize everything in workstations or work areas that must include the following utensils:
- a heating area to melt / heat the oils. equipped with 1 thermometer. It can be a microwave or two pans prepared for water bath
- an area to prepare the soap batter, where the bowl with measured oils is already found, the bottle with essential oils and GSE and the cup with dye. It must be equipped with: spoons, a spatula, a strainer (optional), 1 measuring jug, a plate where to put dirty items, some squares of kitchen paper and the immersion blender already plugged and prepared. You can prepare this area next to the heating area.
- an area to mix the water with lye. It is important that this area is well ventilated, ideally outdoors, or under a window. This area should have: a stainless steel spoon or silicone spatula, a thermometer, a large container with cold water to cool the sodium hydroxide solution (caustic soda).
- an area with the molds, and the prepared thermal insulation material (towels, blankets, or wooden boxes). Usually, it is next to the soap preparation area.
Have you noticed what I forgot in the soap dough area?
Yeah, it was the small bottle with the essential oils and the cup with the dye 🙂
It is very easy to forget and then things go wrong. The greater the preparation at this time, the better the production will be, and in the end you will have a spectacular soap to enjoy in your bath!
Step 3: Melt / heat the oils
Is everything ready? So let’s start making soap!
There are recipes that start by melting the “solid” oils (coconut oil, palm oil) over very low heat, and adding the liquid oils as soon as the first ones have melted. I put everything in a microwave-safe pyrex large bowl and heat the oils until small pieces of the solid oils are left and let the rest melt out, mixing.
If you are going to use the microwave, I recommend starting with 2 minutes for 450g recipes, and 4 minutes for 1kg recipes, and then measuring the temperature while setting the microwave to 30 seconds at a time. With experience you will understand what time and power to use. Note that the oils must not be overheated. It is not to throw everything away if it happens, but it must be avoided.
Step 4: Prepare the lye water (sodium hydroxide solution)
Using lye can (and should) be intimidating, however it is a necessary ingredient in soap making. All soaps, even glycerin bases, are made with sodium hydroxide (lye).
While the oils are heating up in the microwave (don’t let them heat up too long unattended), let’s prepare the lye water. From here the clock starts to count!
First, put on your safety equipment: gloves, glasses and mask if there is not enough ventilation. You must have clothes that cover your legs and arms, and shoes that cover your feet. Make sure that there are no children or animals in this area, to minimize the risk of accidents.
Now, be prepared to place the container where you will make the solution (ideally in pyrex or stainless steel) in a container with cold water or on an outdoor surface (a bench, for example). As soon as you mix the lye with water, it will reach temperatures in the order of 80º!
Do not use the refrigerator or an enclosed area to cool the mixture, because of the resulting vapors that are corrosive and toxic.
Safety first: use ALWAYS gloves and glasses at all stages of soap making, especially when dealing with caustic soda or aqueous solution.
Mix water and lye
Water (at room temperature) and lye should now be measured in separate containers. The container with water, where you are going to make the mixture, must be made of pyrex, glass or polypropylene (PP) plastic, that is, resistant to high temperatures and chemical corrosion.
Slowly pour the lye into the container with the water and mix well with the stainless steel spatula or spoon. The solution will heat up and release harmful vapors especially at this time. Be careful and avoid breathing vapors. Mix very well so that the lye completely dissolves in the water. As per recipe, add the dye at this stage.
Note that pouring water over lye can have a “volcano” effect! Always pour the lye over the water.
It is also important to ensure that the water is at room temperature (25º), especially if you are using an herbal infusion. Even if it is only lukewarm, the “volcano” effect can be dangerous. The same applies if you are using milk or sugars in the water.
In the meantime, I’ve felt the need to write a post focused on preparing the lye water alone: How to Make Lye Water. See the simplest way of making lye water in the video below, although you can add colorants or addictives to it, depending on the recipe:
Step 5: Ideal temperatures for mixing – Cold Process
What raises more doubts when making soaps is at what temperature to mix the oils with the aqueous sodium hydroxide solution. Do they both have to be at the same temperature or not?
The temperature at which the mixture is made will affect the soap in color and texture. There are many factors to take into account when choosing the mixing temperature: amount of dough, type of mold, whether there are sugars in the mixture (honey, milk, sugar) and what color you want to achieve.
On the one hand, the higher the temperature, the more intense the color of the soap will be, due to a reaction called “gelling” – “Gel” phase. Typically, I make soap when the oils are between 32-43 ° C, and let it cool down to close to 32 ° if using sugars. The aqueous solution of sodium hydroxide must be no more than 10º away from the temperature of the oils and always below 45º.
If you mix the oils and lye water above 54 ° C, in the cold process, you run the risk of having a wide range of problems with the soap: volcano effect, cracks and discoloration. One of the few exceptions is when using beeswax, but otherwise, we must keep temperatures low. If you want to know more about the effect of temperature on the soap batter, see also this article.
On the other hand, when handling a large soap batch (> 1 kg) soap makers tend to use lower temperatures, close to or below 45º. This is because there is a tendency, when using bar molds, that soap around the edges will get cloder faster than at the center of the mold, which will make the color more intense and darker in the middle of the soap and lighter and more pale at the edges. Soap looks more opaque in the edges and more translucent in the center as well.
Using lower temperatures gives the soap a more homogeneous color and texture. Of course, these are only aesthetic considerations, but many soap makers make soap for sale and a strange aspect makes the soap less salable.
For small soap batches (~ 0,5 Kg) if you want a more intense color, it is preferable to mix between 43º-48ºC. If you want a softer and opaque color, the temperature to be used should be around 38º-43ºC.
When using milk, honey or sugars, the soap dough will tend to heat up a lot and very fast. It will continue to heat even after pouring the soap dough into the molds. That is why it can crack if you are not careful with the temperatures.
If the recipe includes any of these ingredients, it is best to use temperatures always below 43ºC. Above it, the mixture can caramelize and turn brown, which can modify the color and aroma of the soap. You can also use this effect to your advantage.
By this time, the oils should be hot and completely melted. As per recipe, add the dye at this stage, and stir very well.
Check the temperature of the oils and the lye water until both are close to the set temperature and have a temperature difference <10ºC. Usually, what happens to me is that the oils cool down first.
If the lye water cools too much (below 35º), do not heat it! It is possible to use the lye solution at room temperature with the oils still hot, as long as the temperature is above that of the melting oils (“solid” oils still in a liquid state). Adjust the temperature of the oils by heating them again in the microwave or cooling them in the sink with cold water.
Step 6: Reaching Trace
Now the interesting part will begin! Pour the lye water into the oil mixture through a strainer. I have not always used it, but it is a precaution if some lye has not completely dissolved.
Now, insert the immersion blender into the mixture and tilt it to release air bubbles. Turn on the blender for very short periods of time and then mix it up a little, using it as a spoon. The mixture will slowly stop being “oily” and start to take on a more milky and opaque consistency, especially when you switch on the blender.
Repeat these steps with the blender until you reach “trace”, avoiding air bubbles as much as possible. Depending on the amount of fat and the type of oils used it can take from 1 to 15 minutes.
What is the “trace”
The “trace” is when the oils and the lye water solution emulsify completely through the process of saponification. The mixture reaches the point when it gains a consistency similar to the pudding mass but liquid. If you make a straight line inside the batter with the wand, you will see a “dash” that does not disappear soon. I recommend in the first recipes not to go further from here to have a liquid mass easy to pour into the molds.
If you continue to blend the dough, “trace” will stop being light – dough with liquid pudding consistency – and will become heavy trace – dough with mayonnaise consistency. If it reaches the point of heavy “trace”, you must work quickly, or the soap dough may solidify before being in the molds (seize).
The type of “trace” turns out to be a preference of the soap maker: a lighter “trace” (liquid mass) allows the dough to be poured into molds, almost completely avoiding the appearance of air bubbles; Heavier “trace” (paste-like dough) allows to make reliefs, layers and textures with the mass, something impossible with the liquid mass.
Please note that the soap dough, in order to reach the “trace” completely (light trace), cannot have floating oils. We must have a consistent and opaque emulsion. The figure on the left shows the dough without reaching the “trace” completely. The middle figure shows a light “trace”, and the right figure shows medium “trace”.
Note: If you do not use an immersion blender, and choose a hand whisk or spoon, prepare to beat the soap dough for 3 hours until you reach trace…. Hence it is essential to use the immersion blender 🙂
Step 7: Add ingredients after trace
After the soap dough has reached trace, you will have to work quickly to add the most “delicate” ingredients (ingredients to add after trace). These include superfat oils, essential oils, anti-oxidants, dyes, vegetables or spices for texture and others.
These ingredients are added after trace for several reasons: the chemical saponification process generates heat and ends up destroying and evaporating some properties of ingredients more fragile at temperature (some essential oils or extracts, for example); when adding ingredients like poppy or oat seeds, the blender will turn them into powder; superfat oils are not saponified.
Many soap recipes include a superfat oil, that is, an extra amount of oil or even a different oil that will not be saponified.
The amounts of lye and oils are calculated so that when mixed, they are completely transformed into soap and glycerin (“superfat” of 0%). When the quantity of oils is higher, it is said that the recipe contains an oil “superfat” (usually 5% “superfat”), that is, this oil will not saponify and will be present in the soap simply as oil. This makes the soap softer and more moisturizing for the skin.
Many of the recipes I tried include the “superfat” already included in the recipe (when calculating the quantity of oils), it is not necessary to add an oil after trace. This makes the recipe easier to make, especially for beginners.
Add “super-fat” oil after trace
In case the recipe includes an oil for “superfat”, normally a more noble oil, this must be added after trace as already mentioned, avoiding its saponification.
If the oil is “solid” or a butter, you should melt it first before adding it to the soap batter. For easy recipes or while you are a beginner, you should only use liquid oils like “superfat” (sweet almond oil, for example).
Add an antioxidant
In this step, you must add the antioxidant if the recipe asks for it or if you wish. Some soap makers use anti-oxidants, some find it unnecessary. The role of anti-oxidants is to prevent oils that have not saponified (“superfat”) from becoming rancid over time.
There are 3 anti-oxidants that soapmakers use: Grapefruit Seed Extract (acronym: GSE), Rosemary Extract (acronym: ROE), and Vitamin E, each with pros and cons.
Personally, I advise you to always put the anti-oxidant, to avoid getting rancid soap. Note that anti-oxidants are not preservatives. Soaps do not require preservatives, since, after curing, they do not contain water or any other medium where bacteria can breed.
Note: You should be quick in this step, since, depending on the recipe, the dough can harden very quickly. Use a hand mixer to mix the ingredients after mixing, avoiding air bubbles.
Step 8: Pour the soap dough into the molds
The soap dough is now ready to be poured into the molds! See the article How To Make Soap From Scratch for information on which molds to use. I recommend the use of silicone molds in the first attempts. I use this rectangular mold a lot, gives 6 beautiful and simple bars of soap using 450g of dough.
Pour the dough that should be liquid into the mold (s). Then, tap and / or turn the mold (s) carefully so that the dough settles and releases any air bubbles.
Sprinkle with a spray bottle your soap on the whole surface with rubbing alcohol or witch hazel, to prevent soda ash (this was a hard-learned lesson).
Attention: the dough at this point still has lye and may irritate the skin or even burn! Use the safety equipment even at this stage!
Isolate the soap mold
You can now choose to isolate the mold with the soap dough or not.
Isolating will allow the dough to remain warm at a uniform temperature for about a day. Consequently, the soap will go through the “Gel” phase which gives it a more translucent appearance and a more intense color. You can isolate the mold by placing it in a wooden box, or put cling film over the mold and wrap it in a towel or blanket. I recommend always doing this.
If you decide not to isolate the mold, the soap will look more opaque and the color will be paler. If you want to make sure that the soap does not go through the “Gel” phase, you can place the mold in the refrigerator.
But what is the “Gel” phase anyway? When the soap is solidifying in the mold, it heats up due to the continuation of the saponification process, reaching temperatures close to 80º. The soap will have a gelatinous and shiny appearance.
However, to reach this “Gel” phase, the mixing temperature must be between 48ºC and 54ºC and the mold must be isolated. For recipes where the temperature is 38ºC, it is unlikely to go through this phase. If you want to learn more about the “Gel” phase, see this article.
If the recipe contains sugars, it will not be necessary to isolate as the dough will go through the “gel” phase even without insulation. The temperature of the soap will increase more than with other doughts, even after being poured into the mold.
Step 9: Clean up your equipment
When your soap batter is finally setting on the moulds, it’s time to clean up all equipment and the working areas. Still some precautions are needed even to clean up. If you kept your work organised, and worked cleanly, you will have less work to do now.
Check this article with tips and a full explanation on how to clean up your soap making equipment: How To Safely Clean Your Equipment.
Step 10: Wait 24-48 Hours
You must leave the dough in the mold to solidify for at least 24 hours. If you do it too soon, the soap may fall apart and will only have a mess as a result …
The recommendation is to leave the dough in the mold for 48 hours until unmolding. Not only will the soap have completely solidified, the saponification will be complete and the soap is already safe for the skin.
For soaps made only with olive oil, I recommend leaving more time in the molds, from 4 to 7 days, depending on the solidification. If the soap does not solidify within 14 days, then you must have some kind of problem. Read more this article to learn more about it.
Step 11: Unmold and cut the bar soap
If you used these silicone molds, simply unmold the soaps for curing. If you used plastic molds for your soap and have difficulties in unmolding, place the mold in the refrigerator for about 30 minutes. The bar of soap should unmold like an ice cube.
With soap bars, you don’t have to use more than a sharp knife to cut your soap into small bars. If you want more precision in the cut, I recommend to purchase a professional soap cutter, like the one in the image below.
Check out How to Cure Soap.
Step 12: Curing the soap
After unmolding and cutting the soaps, they can appear ready to use, having a very intense and pleasant aroma.
However, they are not yet ready for use, as they need to cure, that is, they need to completely release the water that still exists in its composition and finish the saponification process.
To cure soaps, you need a well-ventilated, cool area, without too much moisture, direct sunlight or extreme temperatures.
Place them on a sheet of wax paper and leave a space between them so that the air can circulate freely. Leave to cure for at least 4 weeks up to 8 weeks. See the recipes.
Mark the start and end date of curing the soaps and be patient. When you realize it, the weeks have passed and you will have your soap ready for use!
I hope this soap making tutorial has been helpful! If you have any questions, please use the comments section.