Things You'll Need:
- Glycerin Water Lye Strainer or colander 3-gallon Tupperware container Stainless steel or aluminum pots to heat ingredients Stove or hot plate
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Step 1
Filter the glycerin. Heat the glycerin to 175 degrees on a stove to burn off any residual methanol or ethanol from the transesterification process and then pass it through a strainer or colander to remove impurities. Glycerin from biodiesel is darker in color than other forms, and though heating and straining won't result in absolutely pure, clear glycerin, it will remove unwanted objects that could be dangerous in a bar of soap.
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Step 2
Mix the water and lye. For every gallon of glycerin, measure out 1 quart of water and 5.5 ounces of lye. While keeping the glycerin warm enough to remain liquid, bring the water to 100 degrees in a separate container, and add the lye. Allow the lye to dissolve completely.
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Step 3
Combine the ingredients. Pour the water and lye into the glycerin. Stir gently for 20 minutes over steady heat.
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Step 4
Cool the mixture. Pour the mix into the large Tupperware container at the desired thickness, usually about 1.5 inches. Cover it and allow it to sit undisturbed for 24 hours.
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Step 5
Cut bars. After 24 hours, the soap will still have solidified somewhat but will still be soft enough to cut easily. Cut around the edges to loosen the soap from the container, then cut the soap into individual bars of desired size. Allow these to cool and sit for another four to seven days. Use wax paper to separate bars while sitting.
