How do you make glycerin?

This clear liquid they sell at walmart for about 2 something for 4 oz.

It is a little expensive. How do you make glycerin?

Glycerin is a natural by-product of the soap-making process. In order to make glycerin, you must make traditional soap. Another term for this traditional soap is lye soap. These directions are very similar to what you would see in a lye soap recipe, but it is altered at the end to separate the glycerin, which will be produced.
Difficulty: Challenging
Instructions


Things You'll Need:

• 2 gallons non-tap water
• 10 oz. of lye
• 5 lbs. of tallow (fat from beef)
• Strainer
• Large pot
• Wooden spoon
• Salt
• Knife

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   Cut the tallow into 1 inch square cubes. Cut off any parts that are not white.
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   Place the cubes of fat into a large pot and let it simmer until all of the grease is gone. Once that happens, pour the contents through a strainer. Your solid pieces of fat should now be an amber color.
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   Put the solid pieces of fat back into your empty pot and add the 2 gallons of water. Put this pot on a medium amount of heat. Make sure the water and fat are well blended before continuing on.
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   Slowly add the 10 oz. of lye into the pot. Continue to stir the mixture until the lye is dissolved.
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   Continue to heat the mixture for about 30 minutes, or until it is very creamy like a soup.
2. 6
   Begin to add salt to the pot. There is not a set amount. It is best to continue sprinkling it until you notice the "soap" portion of the mixture rise to the top. Strain out these solid pieces and distill what's left in the pot. This is your glycerin.

I am sure you can find it cheaper if you search around.