Our definition of natural soap is one made of oils, fats and butters that have been mixed with lye. A completely natural soap should also be coloured naturally as well, to adhere to the definition of a natural soap. Soap is made through the process of saponification. This is where lye (a mix of either Sodium Hydroxide or Potassium Hydroxide and water) is mixed with oils, fats and butters to turn the oils into salts. It is a chemical reaction where the triglycerides of the fats and oils react with the lye. This reaction is an exothermic one, which means that it produces heat. The amount of heat used to produce the soap will determine whether it is hot or cold process soap. Cold process soap is made by as the name suggests keeping the soap cooler. Usually the temperature of cold process soap will be around 120 degrees fahrenheit. Still quite hot, but cooler than the hot process. Cold process soap is easier to pour as it is generally still very liquid when the mixing of the soap has finished. It also yeilds a bar that looks fresh and clean cut and generally more aesthetically pleasing. Hot process soap like the name suggests is made at a higher temperature, which for most soap makers will be around 150 degrees fahrenheit or hotter. Extremely hot and you would know about it if you got any spilt on you.
Hot process soap is less easy on the eye as it is harder to pour into a mould. Let’s just say if you like the rustic look then you will like hot process soap better than the clean cut of a cold process soap. Hot process takes only 1-3 weeks to cure as most of the water has already left it in the process, where as cold process will take from 4-6 weeks to cure. Once the saponification has happened and the raw soap has been poured into the mould, it will take around 24-48 hours for the process to be complete. The soap will then have to cure for a set amount of time which will depend on which process was used but can range anywhere from 1 week to 5 years.