Perfect for those with sensitive skin, this homemade glycerin soap recipe makes a hard bar of soap that lathers nicely while gently cleansing and moisturizing your skin. 
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Homemade Glycerin Soap Recipe (From Scratch)

Perfect for those with sensitive skin, this homemade glycerin soap recipe makes a hard bar of soap that lathers nicely while gently cleansing and moisturizing your skin.
Makes around 8 bars of soap.
Course DIY products, Soaps
Prep Time 30 minutes
Cook Time 3 hours 30 minutes
Total Time 4 hours
Servings 1 kg soap

Ingredients

For the soap

Solvents

  • 120 g glycerin Between 98g and 147g
  • 300 g 70º alcohol Between 275g and 321g
  • 90 g sugar Between 73g and 110g
  • 180 g distilled water Between 147g and 244g

Instructions

Make the soap.

  • Weigh out the lye in a small, non-metal bowl.
  • Weigh out the distilled water in another, larger, non metal bowl.
  • In a well ventilated area, carefully pout the lye into the container with the distilled water. You should wear gloves and goggles to protect your eyes and hands. Stir the lye into the water until it is dissolved. The mixture will heat up and get cloudy at first, but will clear up and cool down with time.
  • Leave the lye mixture to cool while you weigh out the oils. I find that the easiest way is to place the bowl on a digital scale, tare it, add an oil to the bowl until you reach the right weight. You then tare again before carefully adding the next oil, and between each addition.
  • Add the oils to a slow cooker on low heat, and stir them together well. Allow any solid oils like the tallow to melt.
  • Carefully add the lye mixture to the melted oils, and gently stir them together. Once the lye solution is fully incorporated into the oils, you can begin to blend them together with an immersion blender. 
  • Blend with the immersion blender until the mixture thickens to trace. Once the mixture has reached trace, place the lid on the slow cooker and allow the soap mixture to cook for several hours (around 3) until it starts to get transparent.
  • You have now made a hot process soap.
    Perfect for those with sensitive skin, this homemade glycerin soap recipe makes a hard bar of soap that lathers nicely while gently cleansing and moisturizing your skin.

Use the solvents to make it translucent.

  • Weigh out the alcohol and the glycerin. You will be mixing them together and adding them to your soap. I would have liked to use a high proof alcohol like Everclear, but couldn't find anything like that here in Spain. I ended up using a 70º denatured alcohol. they say that if you use a higher concentration of alcohol, that it will do a better job of making the soap more transparent. (Perhaps next time I'll try with a 90+% denatured alcohol. Rubbing alcohol is said to leave an unpleasant scent behind, but I haven't tried it to verify the difference.)
  • Pour the alcohol and glycerin mixture into the soap. You'll probably end up with chunks of soap floating in the liquid. Try to break them up as best as you can. (I used my immersion blender to break up the chunks and fully incorporate the alcohol and glycerin into the soap. Work in a well-ventilated area for this step and be careful not to have any open flames in the area. (You should always be careful when heating high percentages of alcohol.)
  • Cover the crock pot, sealing it as best you can so that the alcohol doesn't evaporate. (If it evaporates too quickly, it won't be able to work its magic on the soap.)
    If you really have your heart set on making a translucent soap, you should seal your crock pot with some sort of plastic wrap before placing the lid on top. I didn't have any on hand, and wasn't really too concerned about making a fully transparent soap, so I just used the regular lid of my crock pot. 
  • Allow the soap to cook, covered and sealed, for around 30 minutes.
  • Meanwhile, make your sugar syrup. Weigh out the sugar and water and mix them together in a saucepan over low to medium heat until the sugar has completely dissolved. Remove it from the heat.
  • Once the 30 minutes has passed, you can begin to add the sugar solution to the soap. Gently mix it in, trying not to move the soap too much so as not to form a lot of foam or bubbles.
  • At this point, you can begin to test the soap for translucence. It will look translucent to the eye, but as it cools, it will become more opaque. The way most people check is by freezing a glass, and adding a small amount of soap to the bottom of the glass to cool it. Keep in mind that you are using a very thin layer of soap, and that when you have a thicker layer it won't be as translucent.
  • To try to get a more translucent soap, you can continue to cook the soap, adding in small amounts of the various solvents and checking the translucence with the frozen glass. (To be honest, I didn't bother, and just added the sugar, and went right to pouring the soap into the mold. Perhaps next time I'll try for a more translucent soap, and will give you my tips for what works best.) 
  • At this point, you can add in any fragrances or colorings. The nice thing about this soap is that because it has been cooking for so long, and has completed the saponification (soap making) phase, you can even use food coloring to color your soaps. You won't have to worry about the lye reacting with the colorants and changing them as often happens when adding things to cold process soaps. 
  • Clear the foam off the soap, and carefully pour the soap into your soap molds. Try to be gentle at this stage as any movement can cause foaming of the soap, which will lead to a more opaque soap. (I wasn't very careful, and my soaps have a more transparent layer on the bottom, with a thin layer that is more opaque at the top, where the bubbly soap settled before hardening.)
    Perfect for those with sensitive skin, this homemade glycerin soap recipe makes a hard bar of soap that lathers nicely while gently cleansing and moisturizing your skin.
  • You can skim the foam off and pour it into small soap molds. They will make a more opaque soap that will work just as well as the rest of the soap.
    Perfect for those with sensitive skin, this homemade glycerin soap recipe makes a hard bar of soap that lathers nicely while gently cleansing and moisturizing your skin.
  • Allow the soap to set undisturbed overnight. 
  • The next morning, check the soap for hardness. If it is hard enough, unmold the soap and cut it into bars as needed.
    Perfect for those with sensitive skin, this homemade glycerin soap recipe makes a hard bar of soap that lathers nicely while gently cleansing and moisturizing your skin.
  • Allow your soap to cure and dry for several weeks. This is best done by separating the soaps to allow for air flow over them. It's a good idea to rotate the soaps occasionally so that all sides dry at the same rate. The curing process will allow it to harden and finish any remaining chemical processes to make for a better soap.
    Perfect for those with sensitive skin, this homemade glycerin soap recipe makes a hard bar of soap that lathers nicely while gently cleansing and moisturizing your skin.