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Soap Basics: Cold Process

This is by far my favorite way to make soap. It combines chemistry and art into this beautiful, fun and useful tool. There are so many adaptations and methods I couldn’t possibly describe them all. So we are going to go over the most simple… Castile soap. I use this for all my kids (it’s even safe for baby) and for washing just about everything around the house. It is one of the most simple and effective soaps out there and totally crunchy approved. 

Materials needed

  • Scale (kitchen scales usually work well) 
  • At least two glass or metal bowls. 
  • Lye (sodium chloride) 
  • Distilled water (found in the baby isle at your local grocery)
  • Olive oil (Pure and fresh if it’s not then it won’t be as pretty or nice smelling)
  • Rubber gloves
  • Eye protection
  • Long sleeves (extra layer of protection)
  • Vinegar (just in case of a spill, vinegar neutralizes lye) 
  • Crock pot or double boiler
  • Soap mold
  • Stick blender
  • Stick Thermometer
  • Time without small children (lye is caustic do not use around little ones)



Olive oil 24 oz 

Distilled water 7.68 oz

Lye 3.09 oz


  1. Prep your area and don your safety equipment (gloves, long sleeves, eye protection). Have your vinegar close by and open just in case. Have everything together and ready to go we don’t want to be looking for anything with caustic chemicals in play. Please read through instructions carefully before you start. 
  2. First let’s mix the lye and water. Measure out each with your scale then combine. Remember add lye to water not water to lye. Water splashes lye doesn’t. Do not have your head close to  the gas that this combo give off. I like to mix these on my stovetop with the fan running. It WILL burn your eyes. The gas only lasts a second. Then put the thermometer in. Set the whole thing aside we want it to get down to about 110 degrees F. 
  3. Next we start on the olive oil. We want the lye water combo and the olive oil to be with in ten degrees of each other. Measure out your olive oil and heat it either in a crockpot or in a double boiler. The goal is to get it to 110 degrees as well. It can be a little less as long as it is with in ten degrees of the lye water. 
  4. While you wait you can prep your mold or if you want to add any fragrences or color you can measure that out. For your first batch I recommend not adding anything just do the basics then experiment with fragrances and colors later. 
  5. When the temperature of both the lye water and oil are within ten degrees of one another then you can mix. I pour my lye water into my oil. Using the stick blender I mix the two. You want to mix until what is known as saponification happens. It is were you can trace with a spoon and see where the spoon has been.​
  6. Once saponification happens you can add your colors  or scents. I didn’t add anything to my batch this time.
  7. Pour  your solution into the mold. I like to hit the side of the container lightly to settle the solution into the corners. Then set it out of the way to harden. 
  8. Once it hardens you can remove it from its mold. This usually takes 24-36 hours. I used a silicone loaf pan so I then cut my soap into bars. I cut mine about an inch and a half wide. I measure and mark both sides then cut. 
  9. Once you have your individual soaps they need to cure. I use a wire rack so they can get circulation on all sides. The curing process can take a pretty long time, up to a year. This recipe uses a lower water to oil ratio so it won’t take as long. These should be fully cured in a month to 6 weeks. 

0 thoughts on “Soap Basics: Cold Process

  1. Making things like soap, tooth paste, shampoo and such with like really cool ingredients actually seems pretty neat 🙂

    1. I really enjoy making things myself and learning the process. I plan to have several more how-to’s in the future.

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