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Cold Process Vs Hot Process Soap – The Best Process As Per Experts


Handmade soaps are different to one another because it all comes down to the nuances of the soapmaker. The designs, the ingredients and personal predilection play a huge role in this unique work of art. And every new soap-maker faces the same conundrum- which soap making method to use.

Those newbies who feel conflicted need not stress too much about this problem, because every soap making maestro has once in his or her professional life has faced this dilemma. Soaps are made with different techniques. It includes: -

  • Cold process soap making
  • Hot process soap making
  • Melt and Pour process soap making
  • Rebatch making soap
  • Hand-milled soap making

Out of these methods, cold process and hot process soap making are the most popular and widely used methods. Both processes have its similarities and differences, and pros and cons. (As we proceed with the soap making process and soaps we will encounter some jargons which will be explained briefly.) What’s the difference between cold soap-making process and hot process soap making?

Cold process method and hot process soap making offers the soapmaker with personalization preferences. Perfecting both the process will give a choice of formulating unique soaps with different oils, aromas and texture.

Understanding Cold Process Vs Hot Process Soap Making

Cold Process Soap Making

The basic principle of cold process soap making is mixing the oils together with sodium hydroxide (an inorganic compound commonly known as lye and caustic soda). Mixing the oils with lye will result in a chemical reaction known as saponification. Saponification is a process of using alkalis and changing esters to soaps and alcohols.

The soapmaker chooses the oils, the aroma, the color additives (colorants) and other substances used in making homemade soap. The cold process soap making is beginner friendly and a good way to start making soaps.

There are several ways of making soaps. The ones made with cold process are supposed to be mild or gentle soaps. The method of cold process soap making uses organic ingredients including carrier oils and essential oils, which results in a gentle soap. These so obtained soaps are suitable even for those with sensitive skin types with good moisturizer. The cold processed soaps are cured for a month or month and a half.

Benefits of Cold Process Soap Making

  • The cold soap making process retains the structural and chemical integrity of most ingredients. Some of the components used in soap making are Shea butter, carrier oils and essential oils. When these ingredients are heated, they might lose some of their therapeutic properties. There is no such worry in cold process.
  • The soaps made via the cold process have a creamier lather. The process uses all organic ingredients including oils and butter that ensures overall moisturization. The soaps made through the cold process also have better permeability, which along with its moisturizing qualities treats dry skin issues and soothes irritated skin.
  • Aromatic essential oils are often added during the soap making process. The blends of essential oils transmit an aroma that becomes the distinct quality fragrance of the soap. The soaps that are cold processed are cured for many weeks and the aroma of these oils infiltrates every molecule and enhances the fragrance of the soap.

Disadvantage of Cold Process Soap Making

  • The compound sodium hydroxide lye is potentially dangerous. It is used as an ingredient in cold soap making process. If handled or used carelessly it can cause adverse reactions.
  • The entire cold process soap making is time consuming as it can take anywhere between 4 weeks to 8 weeks to complete (the standard is 4-6 weeks).
  • Colorants are sometimes mica based. These colorants may distort the pH levels during the soap making process.

Hot Process Soap Making

As the name suggest, hot making soap process involves heating the soap. This is the main difference when it comes to cold process v/s hot process soap making. In cold process soap making no external source of heat is used. The heat is internally generated by the ingredients and the process of saponification. (The heat further speeds up the saponification process.)

In the hot process of soap making an external heat source is used to heat the soap till it gets to its gel phase. This gel of the soap is then casted into a mould. In the cold process, the saponification generates heat, but this heat need not transform the soap into the gel phase. (It may or it may not.) However, the process of saponification will be faster with the heat.

Benefits of Hot Process Soap Making

  • The hot process soap making involves complete saponification before the solution is poured into a mould for hardening. The faster rate of curing is better. The time taken for curing depends upon the water used in the process. Generally, two weeks is sufficient for the soap to harden before packaging. As a comparison, cold process soap making takes up to six weeks for curing. And if only single-color is chosen, then the process time can be brought down to one week.
  • The lye in cold process soap making is the deciding factor regardless of the super fat the manufacturer needs. In hot process of soap making, after saponification, super fats can be added. And only a smaller amount needs to be added for the aroma because it is added after saponification, and hence does not fade. The benefits of the natural ingredients are retained.

Disadvantages of Hot Process Soap Making

  • Hot process soap making results in thick texture of the soap. The techniques including swirls and overlaying are hard to do on thick texture.
  • This is not much of a disadvantage, but rather personal preference of the customer. The hot process soaps have a rough surface or texture compared to cold process soaps. Some may like it, while others may not.

Similarity Between Cold Process Soap Making and Hot Process Soap Making

Now that we have understood the pros and cons of both methods, let’s look at the similarities of both into hot process soap and cold process soap.

The Need For Lye

Both hot process soapmaking and cold process soapmaking need lye. (In case you haven’t forgotten, lye is sodium hydroxide or potassium hydroxide.) It is a caustic alkali and needs to be handled with extreme care. Why?

Because, it can produce miasmic fumes; it can also harm the eyes and skin, and damage the clothes. One mistake that beginners often make is adding water to the lye. This is a big no. Lye should be added to water. Whether one chooses hot process soap and cold process soap understand lye safety.

The Melting of Fats and Oils

The homogenous melting of oils and fats is common in both processes. This melting process is the only time heat is used in the cold process. Coconut oil may be used in the processes.

Mixing Oils and Fats To Lye

In both the process, oils and fats are mixed with lye solution or flakes when both their temperatures reach the same degree. This mixing is done for emulsification. Hot and cold process bar soap with natural ingredients is saponified in slow cooker.

Tools and Supplies

Hot process and cold process both use similar equipment. One of the reasons is lye. The lye protection equipment includes goggles, mask and proper full sleeves clothing. It also requires a safe area to work and operate. The utensils, pots and other containers must also be of materials that do not react with lye. Then weighing scale and blenders are also needed.

Why Experts Prefer Hot Process Soap Making Over Cold Process Soap Making

Process Simplicity

The hot process soap making is an old way of making soap. But, this traditional method is still preferred by many as it supplies the skin enough nutrients and ably does the job of hydrating the skin. The hot process does not damage the nutrients of its ingredients because most ingredients are added after the process of saponification.

Quicker Curing Time

As mentioned in the benefits of hot process soap making, the curing time is smaller compared to cold process. Allowing the soap bar to cure for a week will improve the quality of the soap once it hardens. The process of soap hardening takes about a day and the resulting soap is long lasting. The cold process soap takes longer curing time, around 5 to 6 weeks; and the resulting soaps are ready to use after a few days.

Better Skin Nutrition

The mixture of fats, oils and lye in hot process soaps nourishes the skin efficiently. The soaps made from hot process moisturize the skin as well as nourishes and cleanses the skin. The lather produced by hot process soaps are more than that produced by cold process soaps.

Why is Hot Process Soap Nutritious?

This is a valid question because we know that heat destroys the chemicals and nutrients in the herbal juices, fats, essential oils and plant purees that are added to the soap making process. The reason why these ingredients retain its qualities is because they are added after the chemical reaction has completed. The lye is cooked completely before adding other ingredients to it.


Cold process soap making Vs hot process soap making is a hot topic in the world of soap making. Choosing one over the other is not an easy task because both have their advantages and disadvantages. The process of saponification and the metal hydroxide lye are used in both processes.

The method chosen for making soap finally comes down to the manufacturer. Cold and hot process method of soap mixture is the most popular methods.

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