Commercial Glycerin

• Vegetable glycerin is sold by many natural foods companies and is found at health food stores, vitamin stores and online. Typically, this glycerin is derived from vegetable oils and is sold in sizes from 4 oz. to 1 gallon. Vegetable glycerin is added to foods to provide them with a sweet taste. As of April 2011, glycerin typically costs $2 to $5 for each 4 oz. container. Glycerin is also found at medical supply stores.
  
  

Vegetable and Animal Fats

• Glycerin is derived from the triglycerides found in plant or animal lipids. Plant lipids are typically unsaturated, since plant foods contain less saturated fat than animal foods. Unsaturated fats are typically liquid at room temperature, much like canola or olive oil. Animal lipids often contain more fatty acid than plant acids. Animal glycerin is derived from animal fats. In most cases, animal fats must be refrigerated or they spoil and lead to an unpleasant odor. In most cases, animal fats are solid at room temperature.
  
  

Deriving Glycerin from Fats

• In order to use glycerin in order to make soap, you must break down the animal or vegetable fats. Use safety precautions when breaking down glycerin, such as wearing rubber gloves and safety goggles. To break a fat into glycerin, heat 2 cups of animal or vegetable fat, mixed with 1 cup of water. Add about 1 tbsp. of lye and stir the mixture for 20 minutes. Keep the temperature at about 125 degrees Fahrenheit, then reduce it to 100 degrees and continue stirring for 30 to 45 minutes. Remove the pot from heat and wait for the glycerin to form at the bottom of the pot. Soap forms at the top of the pot and must be removed by scooping it off the water.
  
  

Synthetic Glycerin

• Synthetic glycerin is created in a laboratory by mixing certain chemicals with petroleum. It is unsafe to use synthetic glycerin in food products, but it may be suitable for certain cosmetics. In most cases, synthetic glycerin is difficult to purchase for at-home soap making, but you may be able to find synthetic glycerin online.