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Soap Making Process: All About Cold Process Soap

A brown, Clove scented fragrance oil bottle places near neutral tones of cold process soap.


Last month, we discussed the basics of Melt & Pour Soap and everything you need to know for the beginner soap-maker. Today, we are moving along with our soap making series and sharing all about cold process. Make sure to follow along below if you want to learn about the fundamentals of cold process and some tips from us at P&J!


Cold process soap is developed through combining oils and sodium hydroxide lye which causes a chemical reaction called saponifaction. Through this saponifaction, you are able to choose which scents, colorants, oil, and any other ingredients to add to your recipe. It’s also a great way to customize your design which you are unable to do using other methods like melt and pour.

CP is also different from melt and pour because you can choose the exact ingredients you want in your soap. Additionally, melt and pour tends to sweat because of the excess glycerin. Whereas, cold process stays firmer when it is completely cured and ready to use. 


Here is a quick list of pros and cons of cold process, if you are thinking of making your own:

  • Freedom to choose what you want in your soap like natural ingredients such as goat milk.
  • As CPS cures, the fragrance intensifies and holds well throughout its shelf life.
  • Able to alter the trace of cold process for various designs like swirls or peaks.
  • When using this type of soap, it can lather well on your skin.
  • Can place additives like flowers or herbs in the thick batter and it will hold.
  • If you want, cold process can be completely all-natural with what substances you add.
  • Sodium hydroxide lye can be dangerous if you do not understand how to properly use it. 
  • CP takes very specific temperatures; oils need to be within 10 degrees before combination.
  • This type of soap takes about 4-6 weeks to completely cure.
  • Colorants can change when added into a high pH condition.
  • Fragrance can have a negative reaction which causes seizing or ricing in the soap.
  • *we recommend experimenting with our oils in a smaller batch for testing CP


Here are a few tips you should consider if you are new to the cold process development: 

Understand the Terms

Gel phase, trace, curing, soda ash, and lye safety are a few terms you must know before starting the cold process soap method. We will quickly define each one of these:

Gel Phase

Gel phase is a preferred look that some soap-crafters strive for. To evoke a shiny look, you can heat the resting soap mold with heating pads or blankets. On the other hand, if you want a matte design, you simply speed the gel phase by placing the finished molds in the freezer.


Trace is the time period when the oils and lye water are emulsified. As the soap sits, the trace begins to thicken. 


Curing is the process of letting the soap sit and harden on its own. This process can take up to 4-6 weeks in a dry, cool, and darker area. 

Soda Ash

Soda ash develops an uneven film across the soap. This occurs when there is an excess of carbon dioxide in the air. 

Lye Safety

Lye safety is necessary to understand when working with this substance. If lye is placed directly on the skin, it can sometimes burn. It is important to wear protective gear such as glasses, gloves, long sleeves, and long pants to protect your skin. 

Understand the Ingredients

Oils, fragrances, digital scales are just a few ingredients that you must know before starting the cold process soap method. We will quickly define each one of these:


Olive oil, rice bran oil, or canola oil are great options for cold process soap. Each of these oils provide a great lather and moisture for the skin. You can experiment with any of these oils to find the one that works best for you and your skin.


Fragrances oils which contain vanillin content will tend to discolor cold process soap. For example, our P&J Candy Corn needs a vanillin stabilizer so it does not discolor the CPS. Additionally, when considering scent hold, CP is a harsh environment as it goes through several pH changes. For example, coconut fragrances can tend to be light in these types of soaps. Some like to use kaolin clay in the cold process method to help hold a given scent. 

Digital Scale 

A digital scale is imperative for the cold process method. It is important that soap-making ingredients are measured carefully in order to develop a balanced soap bar. 

As always, we encourage experimentation with different batches of cold process soaps and fragrance oils!