Cold Process Soap: Process and Benefits

Soap-making has gained popularity among DIY hobbyists and recreational artists in recent years. It started from blogger and social media influencers sharing their pastime crafts in their blogs, Instagram and “How-To” Youtube videos. The rave catched on because

  • The soap-making process is not difficult. It can be simplified to allow soap to be home-made. One can easily follow videos or blog tutorials and start making their own without hours of practice, failure and trial-and-error.
  • It is relatively cheap without a heavy capital investment in equipment. Some of the ingredients can be found in daily staples in one’s own kitchen.
  • It has a simple and easy to follow main procedure, but one can unleash her creativity to produce variants with different color and flavour, personalizing a unique recipe for showing off in social media.
  • Its low barrier of entry makes it a popular choice for kid’s craft activities in family time.

But the word most often heard in hobbyists’ soap-making is “Cold Process”. Why is it called the “Cold” process and not the “Hot” process? How are you going to benefit from using a “Cold” process soap?

What is Cold Process Soap?

“Cold-processed soap is soap made without any outside source of heat.” The word “cold” here does not refer to a specific temperature, such as 0 degrees or sub-zero zone of temperatures. “Cold” here is a physical description of “no heat is applied from an outside source”.

According to the U.S. Food and Drug Administration (FDA), Soaps are “alkali salts of fatty acids”. The process is called saponification, in which soap is made by adding a (strong) alkali to fats and getting soap as a result (with Glycerin as a by-product).

The common strong alkali used in soap-making are usually Sodium Hydroxide (NaOH), also known as “caustic soda”. Soaps made from using caustic soda are typically hard, commonly seen as “bar soaps”. The other commonly used strong alkali is Potassium Hydroxide (KOH), also called “caustic potash”. Potash soaps are soft and can be in liquid form and are commonly seen as “liquid soaps”. Both “caustic soda” and “caustic potash” are commonly called “lye”, and soaps made using them are called “lye soaps”.

When lye is added to fats, the chemical reaction (saponification) takes place and heat is emitted. In “Cold Process”, only the heat generated from Lye’s chemical reaction with fats is used to fuel the production of soap, without an external source of heat being applied.

Why is Cold Process Soap better?

From above we know that the process of soap-making, called “Saponification”, is by mixing Lye and Fats. Fats is the various beauty ingredients we add to the soap to enhance its beautifying properties. Thousands of years ago, man used animal fats such as beef and mutton (referred to as “Tallow”) and the resulting soaps were called “Tallow Soaps”. There were lard soaps from pork, and whale fat was used commonly up till the 17th Century. In recent years, plant and herbal oils have become the mainstream fat ingredients in soaps. This is because along with their oil, there are traces of vitamins, proteins and omega and their plethora of skincare benefits.

However, these organic ingredients are prone to heat. Excessive heat will break down their molecular structure, rendering them ineffective. By making the soap in “Cold Process”, i.e. without an external heat source, these ingredients are largely intact and their potency preserved, and the soap user can get the maximum benefit from them.

Cold process soap vs. hot process soap

Contrary to the cold process, the hot process employs heat to manufacture soaps. The hot process involves mixing fats with alkali and exposing them to an external heat source with a high temperature of around 90 ° C for coagulation. The process does not need drying out and is ready to use as an end product, because the process of saponification is accelerated by heat.

Many soaps shelved in pharmacies are made by hot process. It is suitable for mass production because it is cost effective, has a ready-to-use production base, and reduces production time. However, hot method is not good for the quality of the soap. The fat and oil components lose their nutrients because of the high temperatures, and thus the soap fails to improve the skin health.

Whereas, in the cold process, the end product of the process takes two months to become suitable for use (six months in the case of BLACK PAINT soaps). Therefore, BLACK PAINT soaps command a higher price and cannot be produced on a mass scale. But our soaps have the potency to address skin issues because of the intact organic ingredients.

Downside of Cold Process Soap

Heat speeds up chemical reactions and the absence of external heat results in Cold Process Soaps taking a much longer time to be made. Compared to “Hot Process”, “Cold Process” takes 4 to 6 weeks for the soap to “cure”, before the chemical process is completed. Especially in BLACK PAINT, because of the vast amount of herbal oils (an average of 30 types of oils in our soaps), our soaps are cured over a period of 6 months. Prolonged manufacturing time increases the difficulty for mass production. With higher cost, Cold Process Soaps are generally more expensive.

Upside of Cold Process Soap for BLACK PAINT

Especially so for us in Japan, big manufacturing companies focusing on lowering cost and maximizing volume avoid “Cold Process”, because it is just an un-economical line of business for them. This leaves a market gap allowing specialized companies and boutique workshops (referred to as 工場 こうじょう koujyou), which focus on quality instead of quantity, to thrive. BLACK PAINT is one of them. Founded in Kyoto, a original capital of Japan and the hub of Japanese tradition, BLACK PAINT is blessed with a community of “syokunin” (職人 しょくにん), artisan craftsman who dedicate their lives to hone into perfecting a product. Years of experience and knowledge brings their soap efficacy to an acuminate peak. Because of this dedication, BLACK PAINT has achieved the 10th consecutive year of The Grand Gold Medal of Monde Selection Award in 2019. This award is a globally renowned award run by the International Institute for Quality Selections in Belgium, equivalent in difficulty to maintaining a 3-star Michelin accolade for 10 continuous years.

How BLACK PAINT uses cold process to make soaps?

BLACK PAINT custom crafts each of its 4 signature soaps based on their targeting skin concerns. Each soap’s ingredients are chosen from more than 100 flower and vegetable extracts and oils that are used in our brand. These organic ingredients are included to fight various skin concerns like dryness, sensitivity, acne, aging, etc. These ingredient oils are mixed with caustic soda (referred to as “lye” below). The resulting solution contains soap, glycerin, leftover fatty acids and alkali.


Because BLACK PAINT tries to pack as much of these plant oils (fats) into our soaps as possible, the amount of fats in comparison to lye is definitely excessive. This results in “superfatting” the soap, with 2 additional benefits.

  • Lye is a strong alkali and it is likely to create irritation on the skin. However, the presence of it in the end product is minimal, because the excessive fats will consume almost all the lye in the chemical process.
  • Excessive plant oils and fats will assure there is leftover of these nourishing and humidifying nutrients, making the soaps extraordinarily packed with goodness.

*Superfatting – means that there are more fats than the quantity needed to react with the lye.

Salting-out in soapmaking

Salting out is a process to extract high purity soap from the resulting soap solution of the previous saponification process. BLACK PAINT performs a limited version of salting out.

After saponification, the soap solution has soap dissolved in water. Soap dissolves in water by wearing water molecules like clothes. When salt is added to this water, it separates into sodium ions (Na + ) and chloride ions (Cl − ), these ions also wear (attract) water molecules. As more salt is added, water molecules become insufficient.

When that happens, the salt will begin to deprive the water molecules that the soap in the same water has. Soap has a weaker power to attract water molecules than salt, so the more salt there is, the more soap will be deprived of water molecules.

Soap that has been deprived of water molecules can no longer be dissolved in water and can only come out as a solid (precipitation). In this way, when all the water in the soap is taken away by the salt, all the pure soap contained in the mixture comes out precipitated.

In other soap brands, this salting out process is repeated many times to thoroughly remove impurities to make a high purity soap. The mixture of “saponification” and “salting out” process is able to make high purity soaps with a pure soap content of 98% or more, effectively removing impurities. But the demerit of salting out is that the resulting soaps contain high salt content. That is the reason when the customers get other brands’ soap water into their eyes, they experience a stinging feeling. It is the same as swimming in sea salt water, giving them an unpresent user experience.

Nonetheless, other brands claim that if the salting-out is not carried out completely, the end product (soap) will be impure and contains unreacted oil. Some consider glycerin, a product of the saponification process, to be an impurity that should be taken out from fully salting out. Because Glycerin makes the soap unable to produce enough lather and not serve its cleansing purpose properly. Furthermore, the soap will deteriorate faster because the impurities in the soap decompose.

BLACK PAINT maintains its decision not to do thorough salting out because of 2 unique advantages we have:

  • Salting out is needed to remove impurities from the end product. BLACK PAINT uses premium quality plant oil and ingredients sourced all over the world and the necessity of filtering impurities is trivial.
  • Salting out removes Glycerin, which is a beneficial byproduct of the saponification process. Glycerin is a powerful organic and natural humectant. Its strong capability to retain moisture make it an excellent moisturizer in the soap. Compared to other brands of soap which customers complain of dryness after using, soaps in BLACK PAINT give significantly less “tight” or “dry” feeling after face wash, thanks for its Glycerin.

However, the below reasons are why BLACK PAINT choose to use a limited version of salting-out:

Benefits of cold process soap for the skin

Retain purity and potency of organic ingredients

Since the cold process doesn’t involve external sources of heat, the organic ingredients remain pure and potent. Heat tends to destroy the structure of organic compounds rendering them useless. BLACK PAINT’s cold process soaps use a wide variety of natural oils, extracts and herbal essences for overall skin health. Many of them are sensitive to heat. The cold process preserves these natural ingredients in their pure and potent form.

Moisturize skin instead of drying it up

Cold process soaps do not contain detergents that tend to dry out the skin by stripping away its natural oil. In fact, the natural oils used in BLACK PAINT’s soaps restore the skin’s natural moisturizing factor to strengthen and protect it.

Resolve specific skin troubles

Specific natural ingredients such as charcoal powder, green tea powder, pearl powder, silk powder, etc. can be added along with the natural oils during the cold process. These ingredients effectively fight skin issues such as dryness, acne, aging, sensitivity etc.

BLACK PAINT Soap with box on silk clothBlack Paint Soap

This product is a deep-pore cleanser that targets clogged pores and helps with acne and blackheads. Its main ingredient is Kishu Binchotan Charcoal, which has strong cleansing powers. It cleans out the pores by extracting the debris and its 30 types of organic plant oils help moisturize the skin on the go. Its probiotic content helps mitigate inflammation and mitigates bacterial activity.

Soak the Black Paint Soap in warm water. Apply it directly on the face when its surface melts. Massage with your hands for 30-40 seconds and then rinse. Put the soap in a cool place and let it dry. Also, keep the soap away from humidity and heat.


Reduced pollution causing manufacturing process

Cold process soaps are more environmentally-friendly as they don’t contain detergents. Detergents contain phosphates that interfere with aquatic life leading to algal blooms and oxygen depletion in water bodies.

Natural in fragrance and appearance, no synthetic elements

Cold process soaps are powerfully natural – they look, feel and smell it! The cold process preserves the color and natural scents of the organic ingredients so that the end product isn’t just pure but also aesthetically appealing, great to touch and use as well as naturally fragrant.

BLACK PAINT’s soaps are absolutely 100% free of artificial fragrances which are harmful skin and overall health.

BLACK PAINT acknowledges the demerits of the cold process method, i.e. mass production is not possible since the method is labor-intensive, and soaps produced from the method are expensive. However, when weighed against the benefits, BLACK PAINT’s choice of cold process in soap making is extremely beneficial.


Dr. Unber Shafique

Dr. Unber Shafique is a public health specialist and a freelance medical and health writer. She is passionate about writing health content that supports, educates, and empowers the readers. She believes in sharing thoroughly-researched, easy-to-understand health information. Visit Dr. Unber's website at or contact her at [email protected]