The Cold Process Method to Make Soap

A woman making organic soap at home to sell online
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Making soap is a straightforward process that uses ingredients and tools you may already have in your kitchen. Anything you don't have is available from soap-making suppliers online or some craft stores. The basic method of making soap from scratch is called cold process.

Warning

Start by putting on the safety goggles and rubber gloves. Lye is a caustic and dangerous chemical that can cause serious burns.

What You'll Need

Equipment / Tools

  • Safety gloves
  • Safety goggles
  • Soap pot
  • Kitchen scale
  • Glass pitcher
  • Mason jar with lid
  • Plastic pitcher with lid
  • Thermometer
  • Measuring cups
  • Spoons
  • Spatula
  • Stick blender
  • Molds

Materials

  • Lye flakes
  • Distilled water
  • Oils (types specified in your recipe)
  • Fragrance (optional)
  • Color (optional)
  • Additives such as flower petals, natural exfoliants, and spices (optional)

Instructions

  1. Measure the Water and Lye

    Place a pitcher on the scale and zero out the weight. Add distilled water to the pitcher until it weighs the amount called for in your specific recipe.

    Place a mason jar or plastic pitcher on the scale and zero out the weight. Add the amount of lye called for in your specific recipe. Close the lid tightly and set it in a safe place.

    Warning

    Static cling can cause lye flakes to fly up and stick to your gloves or shirt sleeves. If this happens, remove the flakes immediately.

  2. Mix the Water and Lye

    Slowly add the lye to the pitcher of water. Do not do it the other way around, and don't make any splashes during the pouring. Stir the mixture gently until the lye is dissolved. The mixture will heat up, which is expected. Immediately rinse the tool you used to mix. Put the lid on the lye-water pitcher and set it in a safe place away from children, pets, and other adults.

    mixing a solution for soap
    Mixing the Brine-Lye Solution. David Fisher
  3. Weigh the Oils

    Put the soap pot or a glass pitcher onto the scale and zero out the weight. Following your recipe, weigh the oils one by one into the pot or pitcher. Zero out the weight after you measure each oil. Pour it slowly—you can always add more, but once the oil has been added, it's combined in the mixture.

    Tip

    Weigh the solid soap making oils like coconut, palm, cocoa butter, or shortening in the soap pot. Weigh the liquid oils like olive, sunflower, canola, or castor separately in the glass pitcher and set aside.

    Weigh the Oils You are Using in the Soap
    Weigh Your Oils. David Fisher
  4. Heat and Melt the Oils

    Place the soap-making pot with the solid oils on the stove over medium-low heat. Slowly melt the oils while stirring gently. Monitor the temperature with a thermometer. Turn off the heat when the oils get to about 110 degrees Fahrenheit. Keep stirring until all the solid oils are melted.

    When the solid oils are melted, add the room temperature liquid oils to the soap pot. This brings down the overall temperature. You want the oil mixture to be at about 100 degrees Fahrenheit when you add the lye-water.

    Heating the Oils in the Soap Pot
    Heat/Melt the Oils in Your Soap Pot. David Fisher
  5. Add the Lye Solution

    Make sure all the soap additives in your recipe, such as color and fragrance, are ready to go. Place all the spoons, measuring cups, spatulas, and whisks you're going to need nearby. Once you begin, you need to move steadily.

    Grab your handy stick blender but don't turn it on. Slowly add the lye-water mixture to the soap pot. The oils will immediately start to turn cloudy. Using the stick blender as a spoon, but not turning it on, blend the lye-water into the oils. This is the beginning of the saponification process or the chemical reaction that turns your mixture into soap. Set the lye pitcher aside in a safe place.

    Adding the Lye to the Oils in the Pot
    Add the Lye-Water to the Soap Pot. David Fisher
  6. Mix the Oils and Lye

    While stirring the lye water and oil mixture with the stick blender, turn on the blender in short bursts. To start with, blend for 3 to 5 seconds. Then, turn it off and stir some more. Repeat this process and keep blending in short bursts until the oils and lye-water are completely mixed. At this point, it is nearing trace, the indication that emulsification has occurred. 

    To test if the mixture has reached trace, dip a spoon into the mixture and let it dribble back into the pot. If this process leaves a track on the spoon, the mixture is ready, even if it isn't thick yet. If you were to hand-stir the pot of soap, like soap makers used to do, it might take up to an hour to reach trace. With the introduction of stick blenders to soap making, the trace can be reached in a few minutes.

    Blend the Soap Mixture to Trace
    Blend to Trace. David Fisher
  7. Add Fragrance or Essential Oils

    After the soap mixture is completely blended, but before it gets too thick, slowly add any fragrance or essential oils from your recipe to the mixture. Stop stick blending the mixture and just use the end of the stick blender like a spoon.

    Adding the Fragrance Oil to the Soap
    Add the Fragrance or Essential Oil. David Fisher
  8. Add Additives or Extras

    If your recipe calls for additives such as spices, natural exfoliants, flower petals, herbs, or special moisturizing oils, now is the time to add them. As you did with the fragrance, gently stir them into the pot using the stick blender as a spoon. Before you move on to adding the colorant, give the mixture a brief blend with the stick blender to make sure that the fragrance oil and additives are well mixed.

    Adding Additives to the Soap
    Adding any Additives. David Fisher
  9. Add Color to the Soap

    Next, add color to the soap. If you want the soap to be one single color, add the colorant to the pot and stir. If you want to achieve a swirl effect, do the following:

    1. Ladle about 1/2 to 1 cup of the soap mixture into a measuring cup
    2. Add the colorant to that bit of soap.
    3. Hold the measuring cup several inches above the pot and slowly pour the colored soap into one corner of the soap pot.
    4. Using a rubber spatula, swirl the colored soap through the pot. Don't stir too much or you'll end up just blending the color in with the entire batch.

    The color is a variation where soap-making becomes art and where you can create your custom soap masterpieces.

    Adding the Colorant to the Soap
    Adding the Colorant. David Fisher
  10. Pour the Soap Into the Mold

    By now the soap has thickened. Pour the raw soap into a mold, using a back and forth motion to spread the soap evenly. Scrape the last thick bits of soap out of the pot with a rubber spatula. If the top of the soap in the mold is uneven, smooth it out with the spatula. Pick the mold up and gently tap it on the countertop to dislodge air bubbles that may have been trapped in the mixture. Set the soap in a warm, safe place to set up and begin curing.

    The soap mixture heats up as the saponification process starts. If the temperature of the room is chilly, lay a towel around or over the mold to keep it warm and keep the reaction going strong.

    Pouring the Raw Soap into the Mold
    Pour the Raw Soap into the Mold. David Fisher
  11. Clean up and Let the Soap Saponify

    Set the soap in a safe place and leave it alone. It takes about 24 hours for the soap to harden enough to take it out of the mold and slice it.

    Keep your gloves and safety goggles on to wash all the utensils and soap pots with hot, soapy water. The oily raw soap residue that's left in the pan is caustic and can cause irritation and burns. After everything is clean, put all the ingredients and equipment away.

    After the soap has set for about 24 hours, it should be hard enough to unmold and slice. Pop or slide the soap out of the mold. Slice it into the size bars you like and set it aside to cure. The soap is technically safe to use, but it is best to cure it for about four weeks before use.

    After 24 hours, Unmold the Soap and Slic
    Unmold and Slice Your Soap. David Fisher