Cold Process vs Hot Process Soap Making at Home

As a modern homesteader, you can make your own soap to add a little sustainability to your small farm. You can even use your own animal fats, milk, and plants in your homemade soaps. To get started, you first need to understand the differences in making cold process vs hot process soap so that you can decide which is best for you.

What are the Key Differences Between Cold Process Vs Hot Process Soap

Both hot process and cold process soap-making methods have their advantages and can produce high-quality handmade soap. The choice between the two methods depends on your personal preference, time constraints, and specific goals.

Cold Process Method 

Making homemade soap using the cold process method involves mixing oils and lye solution at lower temperatures. The soap hardens over the first 24 hours so it can be cut into bars. Then the soap cures over the next 4-6 weeks so it can be used safely.

Pros to Cold Process Method

Cold process soap allows for more creative freedom in terms of swirling, layering, and intricate designs. The soap remains fluid for longer so that you can create beautiful patterns.

Cold process soap retains the benefits of the original ingredients to a greater extent, as it is exposed to less heat during the saponification process.

​Essential oils, fragrance oils, and colorants may maintain their properties and scents better in cold process soap, making it a preferred choice for artisan and decorative soaps.

​Cold process soap tends to have a smoother, creamier texture, which some people prefer for luxury and decorative soaps.

Cold process soap-making is considered the traditional method and appeals to those who want to follow traditional soap-making practices. It really does make you feel like an old homesteader.

Cons to Cold Process Method

One of the most significant drawbacks of cold process soap is the extended curing time. Cold process soap typically requires at least 4-6 weeks of curing before it’s ready for use. This waiting period can be a challenge if you want to use or sell your soap quickly.

Cold process soap-making can be more complex, especially for beginners. It involves a deeper understanding of the chemistry and variables involved in the process, such as choosing the right oils, calculating lye amounts, and achieving the right consistency to set.

Due to the slower saponification process, cold process soap can sometimes result in unexpected outcomes, such as accelerated trace (the soap mixture thickening too quickly) or uneven color changes.

Cold process soap may have visual imperfections such as air bubbles, soda ash (white powdery residue on the soap’s surface), and potential separation of layers if making multi-layered soaps.

In some cases, cold process soap can experience separation, where the oils and lye solution do not fully emulsify. You end up throwing the whole batch in the trash, and the whole process feels like a waste of ingredients, time, and money.

The initial investment in equipment and ingredients for cold process soap-making can be higher compared to some other soap-making methods, which may deter some beginners.

Hot Process Method

Making homemade soap using the hot process method involves heating the soap mixture to speed up the saponification process. This results in a quicker cure time compared to the cold process method. Allowing it to cure a little longer after cooling will result in a higher quality bar of soap.

Pros to Hot Process Method

Hot process soap typically has a shorter curing time compared to cold process soap. It is usable within a few days to a week after making it, while cold process soap requires several weeks to cure.

Hot process soap-making offers more consistency in the final product, as the soap maker can see the texture and characteristics of the soap throughout the process, making it easier to control.

​Hot process soap often retains fragrances and colorants better because the soap is exposed to less heat and chemical changes during curing.

Some soap makers prefer hot process soap for making soaps intended for rough use, such as mechanics’ soap or gardener’s soap, as it is often perceived as more rugged and less delicate.

Cons to Hot Process Method

While the hot process method in soap making has its advantages, it also has some challenges. Here are some of the cons of the hot process soap-making method:

Hot process soap typically has a less smooth appearance compared to cold process soap. The cooking process can result in a more rustic or “mashed” look, which may not be as visually appealing for some soap makers.

Hot process soap is generally less suitable for creating intricate designs, swirls, and layered patterns compared to cold process soap. If you’re interested in making decorative or artistic soaps, cold process may be a better choice.

Hot process soap can reach trace (the point where the soap mixture thickens) very quickly, making it more challenging to work.

The soap mixture in the hot process method is exposed to heat for a longer period, which may lead to the loss of some delicate fragrance notes and can impact the color of the soap, potentially causing it to darken or change in appearance.

The hot process requires constant stirring and monitoring, which can be more labor-intensive and time-consuming during the cooking phase. You really have to pay attention to prevent scorching or overheating.

The soap mixture in the hot process method is typically thicker, making it more challenging to pour into molds and create intricate designs or shapes. Scooping the hot soap into molds sometimes leaves room for air pockets resulting in crumbly bars.

The Process For Each Handmade Soap

​Both ways of making your own bars of soap at home are easy to do. Here are two basic recipes with instructions to get you started.

Cold Process Soap-Making

Ingredients:

1. Oils and fats (e.g., coconut oil, olive oil, lard, tallow, etc.) – combined according to your soap recipe.
2. Distilled water
3. Sodium hydroxide (lye)
4. Fragrance or essential oils (optional)
5. Colorants (optional)

Equipment:

1. Safety gear: safety goggles, gloves, and long-sleeved clothing
2. A digital kitchen scale
3. Heat-resistant containers for lye and oils (no glass, no aluminum)
4. A stick blender
5. Stainless steel or enamel-coated pot for heating the oils 
6. A silicone spatula or wooden spoon
7. Thermometer
8. Soap molds

Step-by-Step Instructions:

1. Prepare the Workspace: Ensure you are working in a well-ventilated area. Put on your safety gear, including gloves and goggles, to protect yourself from lye burns.
2. Measure Ingredients: Weigh the oils and fats according to your recipe, and set them aside. Measure the lye and distilled water in separate containers.
3. Mix the Lye Solution: Slowly add the lye to the distilled water while stirring. Never add water to lye, as it can cause a dangerous chemical reaction. Stir until the lye is completely dissolved in the water. This mixture will get very hot and release fumes, so do this in a well-ventilated area or under a hood.
4. Melt the Oils: Combine the oils in a stainless steel or enamel-coated pot. Heat the oils over low heat until they are completely melted, and the temperature is around 100-110°F (38-43°C).
5. Combine Lye Solution and Oils: When the oils and lye solution are near the same temperature, slowly pour the lye solution into the melted oils.Use a stick blender to mix the mixture until it reaches a “trace,” which means the soap mixture thickens slightly and leaves a visible trail when you drizzle it back onto the surface. This will take several minutes.
6. Add Fragrance and Color (Optional): If desired, add fragrance oils and colorants to the soap and mix thoroughly.
7. Pour into Molds: Pour the soap mixture into your soap molds. You can use various shapes and sizes of molds based on your preference.
8. Insulate and Set: Cover the molds with a piece of cardboard or a towel to insulate them and keep them warm. Allow the soap to set for 24-48 hours.
9. Cut the Soap: Once the soap has solidified, remove it from the molds and cut it into bars of your desired size and shape.
10. Cure: Place the cut soap bars on a rack or tray in a cool, dry area with good air circulation. Allow the soap to cure for at least 4-6 weeks. This curing period allows the soap to harden and the lye to fully saponify, resulting in milder and longer-lasting bars of soap.
11. Label and Store: After the curing period, you can label and package your homemade soap. Store it in a cool, dry place until you’re ready to use or gift it.

Hot Process Soap-Making

Ingredients:

1. Oils and fats (e.g., coconut oil, olive oil, lard, tallow, etc.) – combined according to your soap recipe.
2. Distilled water
3. Sodium hydroxide (lye)
4. Fragrance or essential oils (optional)
5. Colorants (optional)

Equipment:

1. Safety gear: safety goggles, gloves, and long-sleeved clothing
2. A digital kitchen scale
3. Heat-resistant containers for lye and oils (no glass, no aluminum)
4. A stick blender
5. Stainless steel or enamel-coated pot for cooking the soap
6. A silicone spatula or wooden spoon
7. Thermometer
8. Crock pot or slow cooker
9. pH test strips (optional)

Step-by-Step Instructions:

1. Prepare the Workspace: Ensure you are working in a well-ventilated area. Put on your safety gear, including gloves and goggles, to protect yourself from lye burns.
2. Measure Ingredients: Weigh the oils and fats according to your recipe, and set them aside. Measure the lye and distilled water in separate containers.
3. Mix the Lye Solution: Slowly add the lye to the distilled water while stirring. Never add water to lye, as it can cause a dangerous chemical reaction. Stir until the lye is completely dissolved in the water. This mixture will get very hot and release fumes, so do this in a well-ventilated area or under a hood.
4. Melt the Oils: Combine the oils in a stainless steel or enamel-coated pot. Heat the oils over low heat until they are completely melted, and the temperature is around 160-170°F (71-77°C).
5. Combine Lye Solution and Oils: Slowly pour the lye solution into the melted oils. Use a stick blender to mix the mixture until it reaches a thin trace, which means the soap mixture thickens slightly and leaves a visible trail when you drizzle it back onto the surface.
6. Cook the Soap: Transfer the soap mixture to a slow cooker (crockpot). Cover and cook on the low setting for about 1-2 hours, stirring occasionally. The soap will go through various stages, including becoming translucent and forming a mash-like texture.
7. Check for Doneness: To check if the soap is done. Use pH test strips; the soap should have a pH level close to neutral (around 7).
8. Add Fragrance and Color (Optional): If desired, add fragrance oils and colorants to the soap and mix thoroughly.
9. Spoon the Soap: Spoon the cooked soap mixture into your soap molds.
10. Cool and Cure: Allow the soap to cool and harden in the molds for at least 24 hours. Once hardened, you can unmold and cut the soap into bars.
11. Cure: The hot process soap should cure for several weeks to improve its hardness and lather, but you can use it right away if needed. Store the soap in a cool, dry place with good air circulation during this curing period.

What Are The Key Similarities in Cold Process vs Hot Process Soap

As you can see, hot process vs cold process soapmaking use the same ingredients in much the same way in the beginning. Hot process uses an external heat source to quicken the cure time, otherwise, they are much the same.

Your Best Choice in Homemade Soap 

Both hot process and cold process soap-making methods have their merits. Hot process soap offers a faster turnaround time, immediate use, and consistent results. Cold process soap allows for more creative control, better retention of ingredient properties, and smoother textures. Your choice between the two methods will depend on your goals and preferences as a soap maker.

Can You Really Learn to Make Soap?

Absolutely. Just take the safety precautions of protecting your eyes and skin, and choose which recipe you’d like to try. Give it a go, and before you know it, you’ll begin playing with additives for fun soaps.

When you’re ready to make your own recipe, use this simple soap calculator to help you figure out measurements.

Using Essential Oils

Determine the safe usage rate for each essential oil you plan to use. This information can usually be found from the essential oil supplier or in soap-making resources. Usage rates are typically measured in a percentage of the total weight of the soap oils.

Essential oils should be added to your soap mixture after you’ve reached a “trace,” which is the point where the soap mixture has thickened enough to leave a visible trail when drizzled on the surface.

Gently mix the essential oils into the soap mixture using a stick blender or a spatula. Be careful not to overmix, as some essential oils can accelerate trace or cause the soap to thicken too quickly.

Using Milk From Your Homestead To Make Soap

Using your own goat’s milk or cow’s milk to make soap is easy. Simply replace some or all of the water in your recipe with the milk.

To prevent scorching or curdling of the milk when adding the lye, some soapmakers like to pre-freeze their milk into ice cube trays. I like to use fresh milk, and add regular ice cubes to the milk, then add lye. Continue stirring until the ice is all melted and the lye is dissolved completely.

What About Glycerin Soap? (Melt And Pour Soap Mixture)

Working with glycerin soap is pretty simple and doesn’t require handling lye, making it a great option for beginners. Most craft stores have melt and pour soap kits with clear step-by-step instructions for you. They usually have color and scent options included as well.

Frequently Asked Questions for Cold Process vs Hot Process Soap

Here are some other questions that new soap makers often have.

Does Hot Process Soap Need A Preservative?

No. Hot process soap is cured by the heating time in the slow cooker. You can use or sell the hot process soap right away, or it can be stored on the shelf until you’re ready to use it. There’s no need to add anything further.

Do You Stir Hot Process Soap?

Yes. As mentioned in the recipe given, you’ll need to stir the hot soap batter throughout the process.

Does Hot Process Soap Need Lye?

Yes. All soaps need a lye mixture in order to make them into soap.

How Do You Make Hot Process Soap Smooth?

Generally, hot process soap making results in a rough, more rustic looking soap. However, you can try a few things to help take the edges off. 

Adjust the water content in your soap recipe. A higher water content can result in a smoother soap, while less water can make the soap thicker and more textured. 

Use finely ground or powdered ingredients, such as herbs, botanicals, or colorants, to prevent any rough texture in the soap. This can help create a smoother finish.

Experiment with your recipe to find the right balance.

In the end, Cold Process vs Hot Process Soap

Whichever soap-making process you choose, you’ll be well on your way to a more sustainable life in no time by making your own soap.

Happy Soaping!

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