If you’ve done your research on Japanese bar soaps, you probably know that cleansing bar soaps are a staple in J-Beauty routines. In our previous blog post, we explained 6 reasons to love traditional Japanese bar soaps (view the blog post here). They can be used for the face and body, include natural colorings, are eco-friendly, tend to last long, are cost-effective, and there is something for every skin type. Pretty neat, right?

What we didn’t mention previously, however, is that there is more to the traditional cleansing bar soap. In this post, we’ll be explaining the types of soap making processes - the difference between hot process and cold process soap bars, and our recommendations for each.

Hot process and cold process soaps – the similarities

There are actually a few similarities to these two soap-making methods -hot process and cold process. One, they both require the preparation of a lye solution; two, they both require that the oils are prepared, which includes melting fats and mixing them with liquid oils; and three, they both require the lye and the oils to be combined, where at that point the emulsion takes place.

At this point, they might seem quite similar, but let’s look deeper into how these two soap making methods are uniquely different from each other.

What are hot process soaps? What are their benefits?

Hot process soaps are made using a method that involves making soap from scratch by combining a lye mixture with oils and/or fats. The soap mixture is heated to speed up the saponification process. The application of heat means hot process soap bars are ready to use sooner. Also, the batter is usually thicker and is poured into the soap mold after its saponified, then hardened into a bar. 

The additional heat used to create hot process soaps speeds up the soap-making process, which means the soap bars can be cut within one day and used right away. However, if you let the soap sit for another week or so, it allows the bar to harden, giving it the opportunity for the water to evaporate to create a harder, longer-lasting soap bar. Unlike cold process soap, the essential oils, fragrances, and other additives are added after the chemical reaction is finished, which helps preserve the benefits of the natural ingredients and the scents to last longer. Hot process soaps can be made in a slow cooker or double boiler, which also makes for easier clean up. When finished, the soap bars have a more “rustic” appearance which some people may find appealing.

While there are many benefits in the soap-making process, some aspects of hot process soaps can be unappealing to some. Depending on what fragrance or essential oil is used for the soap, the high temperature of hot process can sometimes “burn off” the fragrance, causing the scent to fade. Soap makers may also find that adding fresh ingredients like milk and purees can be difficult as they tend to scorch during the soap-making process. Also, the hot process method is commonly used by companies that mass-produced soaps, and when products are made in larger quantities, companies may not be as thoughtful about the ingredients they include in their products as those that are made with care. And most importantly, heat kills active ingredients, meaning that the high heat used can change the chemical compounds of the active ingredients, potentially reducing the soap’s effectiveness.

What are cold process soaps? What are their benefits?

Cold process soaps, unlike hot process soaps, are not exposed to high heat during the soap-making process, but heated from the inside out. Many cold process soaps rely on natural lye (sodium hydroxide) or other types of alkali. Making cold process soaps allows more flexibility to do swirls and designs within the soap batter before it is poured into the insulated mold, as the batter is much thinner. Soaps that are made using this method will usually end up looking smooth and polished.

One of the main benefits of cold process soap-making is having complete control over the ingredients, having no added detergents which can strip off the skin’s natural oils. Since cold process soap-making doesn’t rely on heat, it is easier to maintain the efficacy of the active ingredients like natural and essential oils. The benefits of natural soap making ingredients like coconut oil, shea butter and olive oil can lessen through the heating process in hot process soap techniques; however, the cold process method ensures these natural ingredients are better preserved.

For a cold process soap, you can choose between essential oils and carrier oils rendered from animal fat or from plant-based oils as the base. The good thing about cold process soap-making is that it is an ideal method to preserve the benefits of plant-derived butters and oils, therefore allowing vegan options. Furthermore, cold process soaps are almost always 100% biodegradable, depending on the ingredients. This is good news for the eco-friendly skincare afficionado.

Finally, soap-making with the cold process method allows for a creamy lather to deeply moisturize the skin, penetrating deep into the pores. And the number one benefit of the cold process method is that being able to choose the oils, vitamins and herbs will allow for a soap bar that is good for different skin types, as no artificial or harsh ingredients are added to the soap.

Are hot process soaps or cold process soaps right for you?

Hot process soaps are for you if…

• You’re on a budget and seek more bang for your buck. Hot process soaps are usually more affordable than their cold process counterparts.

• You like the rustic look and feel of traditional hot process soaps.

• A strong, distinct scent is important to you. Essential oils and fragrances tend to remain truer in scent in hot process soaps, as they’re added at the end of the soapmaking procedure.

Cold process soaps are for you if…

• You want to enjoy the full benefits of natural ingredients like olive oil, rice bran oil, and tsubaki (camelia oil). The heating procedures in hot process soapmaking can cause these actives to lose some of their nutrients, but the cold process method helps to retain their virgin properties.

• You want a soap made with moisturizing dairy products like milk, goat’s milk, and yogurt. These ingredients will eventually go bad in a hot process soap.

• Eco-friendliness is your top priority. The cold process approach not only saves water, but cold process soaps are almost always 100% biodegradable.

You want to enjoy a creamier soap bar and luxurious lather.

Our recommendations

While hot process and cold process soaps both have their respective benefits, it is important for you to decide what is most suitable for your skin type and needs. Right now at the JBeauty Collection, we have a variety of hot process and cold process bar soaps made with unique Japanese ingredients that are gentle to the skin. Check out our Collection page for more information on our bar soap collection!

Mutenka Sekken Hot Process Soaps

Mutenka Sekken Hot Process Soaps are kettle-fired, handmade in Hyogo, Japan. These handcrafted soaps are made of all natural ingredients, and are free from artificial fragrances, dyes, and preservatives. The gentle formulation is perfect for sensitive, dry, or itchy skin, and can be used on the hands, body, and hair. Available in rice bran, lavender, and chamomile scents.

Mutenka Sekken Cold Process Soaps

Mutenka Sekken Cold Process Soaps are handmade by artisans in Hyogo, Japan, and are made of luxurious all natural ingredients. Available in cherry blossom, charcoal, Kobe sake, hinoki, and yuzu scents.