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Hot Process Soap vs Cold Process Soap… What’s The Difference?

Updated: Mar 19, 2023

I have been making soap for 7 years now and I was recently speaking to a friend of mine explaining the main differences between hot & cold processed soap which is what inspired me to write this post.

What I will be sharing is the definition of soap and the comparison between the two distinct ways you can make it.

Funny enough, most of my life, I really didn't even know what soap was. I just knew that this magical product would get me clean and that was good enough for me, but growing up with the worst acne, not understanding my skin, and having kids who also struggled with the same made me more curious about products and what they do for our skin. This led me down a path I would of never imagined and that's getting into skin care. What I would soon realize was that I would fall in absolute love with making soap!

What intrigued me the most is learning about what soap actually is and how it could benefit not just one skin type but ALL skin types. Formulating recipes made me feel like a scientist ready to save the world from skin problems! I was intrigued, I was inspired and something about creating something all on my own brought an infinite amount of purpose which would later unleash my potential around being a full on " Creative" of all things handmade.

Okay, so let's get into it:

What is soap?

Soap is the product that results from the chemical reaction that takes place between fat (for example, plant oil, butter or animal fat) and a strong alkali (for example, sodium hydroxide, potassium hydroxide or calcium hydroxide), also called ‘lye’.

Soaps are produced via a process called saponification, a reaction between triglyceride and lye.

This creates glycerin (glycerol), and a salt of fatty acids, which is soap. When lye reacts with the triglycerides found in oils, the fatty acids in the triglyceride molecule are released from the glycerin part. The fatty acids then react with the lye to form soap molecules.

Both cold process and hot process soap bars are produced via a chemical process called saponification, a reaction between triglyceride and lye. This creates glycerin (glycerol), and a salt of fatty acids, which is soap.

Both types of soap can be made from different fats (for example, plant oil, plant butter or animal fat) and a strong alkali, also called ‘lye’.

The main difference between cold process vs hot process soap is that hot process soap is made at higher temperatures than cold process soap.

Cold process soap is made at relatively low temperatures (usually 30-50°C), while hot process soap is made at higher temperatures (usually 50-100°C). This affects the soap making method as well as the properties of the finished soap.

You may be asking yourself which process should you try first. What I would recommend is that if you are new to soap making, learning cold process has its advantages. Cold process soap making allows you to work with lower temperatures and gives you more time to create your soap masterpiece.

Here's some questions you may be asking: What are the main differences between the hot processed and cold processed soap? Which one is better?

I would say It really is a matter of opinion. For me, I like to work with cold processed when I'm trying to make a aesthically pleasing soap and I love hot processed when I'm making a soap that offers specific benefits to solve a specific skin problem.

Here is what I absolutely love about hot processed soap making:

1. Very Quick to make = very economical in terms of time and money

Especially if working at high temperatures, the whole process can be super quick, in less than a hour from start to finish.

2. Shorter cure time = ready to use sooner

Hot process soap bars can be made sooner. With HP soap making, the saponification is finished before the soap is poured into the mold (in cold process soapmaking you need to wait four to six weeks for your soap to cure). However, still allowing your HP soap to cure in 1-2 weeks ensures the benefits are binding .

3. No soda ash

Soda ash is seen as a white ash, on the top of cold process soap. This does not make the soap unsafe for use, but it can be aesthetically unpleasant. Soda ash does not occur in hot process soap. Because the unreacted lye is not in contact with air, the soap does not form soda ash.

4. Easier to Clean

As the saponification is complete when we finish the soap making process, the tools and equipment are fairly easy to clean, since it contains soap and not lots of oils.

5. You have control over superfat which makes a more nourishing soap.

Superfat is ‘extra fat’ that does not react with the lye and turn into soap. It is a portion of fat (oils, butters) that is added to make the finished bars more nourishing. Because in hot process soap making the superfat is added after the saponification is complete, you can control which oils are in the superfat portion, therefore you can control the extra nourishing properties that your soap has.

For example, you can make the base soap recipe using your base oils and then add mango butter as the ‘superfat’ to provide its nourishing properties.

6. Natural Appearance.

HP soaps have a more rustic appearance which are great for the natural look. When I look at HP soap, it instantly makes me go back and imagine how soaps were made in historical times.

Whether you decide on hot or cold process soap making, there is one very important factor you have to consider. Making soap can be dangerous and requires some safety measures. For example, in working with lye, it can burn your skin. No matter what, you need to consider safety first including wearing long sleeves shirts, pants, closed toe shoes, safety goggles and gloves. I would even recommend wearing a mask, because when you first start working with lye, the fumes can be challenging alone.

I hope that this gives you a little perspective on both types of soap making. If you like what you see or want to learn about anything else, join my community and receive exclusive access to my digital library for tools & resources by joining my community below.

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