How to Make Soap From Used Oil

Written by jamie conrad
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How to Make Soap From Used Oil
You can make your own soap out of your used cooking oil. (bars of soap image by Jale Evsen Duran from

Making your own soap is a very useful hobby. Not only can you take charge of what goes into your own personal-care products, you can also save money on them. You can also save money on gifts if you make soap for your loved ones on special occasions. Making your own soap can be simple or tricky and may involve a wide array of different soapmaking tools and ingredients. You can also make soap out of simple household items, such as used cooking oil. Recycling your used cooking oil into homemade soap is a great way to create less waste and get some personalised soap at the same time.

Skill level:
Moderately Easy

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Things you need

  • Flour
  • Used cooking oil
  • Bowl
  • Measuring cup
  • 2 cups
  • Rubber gloves
  • 59.1ml. water
  • 28.4gr. sodium hydroxide
  • Stainless steel spoon
  • Basin of hot water
  • Basin of cold water
  • 2 cooking thermometers
  • Vanilla essence
  • Soap mould (plastic container or gelatin mould)
  • Cling film

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  1. 1

    Pour cooled, used cooking oil into a bowl and cover it with enough flour to coat the surface of the oil. The flour purifies the oil.

  2. 2

    Allow the flour to sit on the oil for one to two days until the flour settles to the bottom of the bowl. Once the flour settles, carefully transfer six ounces of the clean oil into a cup (you may want to use a measuring cup for this step).

  3. 3

    Put on gloves and pour two ounces of water into another cup (stainless steel if available). Carefully add the sodium hydroxide and gently stir until the mixture is transparent.

  4. 4

    Set up two water basins, one full of hot water and one full of cold water.

  5. 5

    Place the cup of oil into the hot water basin (do not empty the cup, just place it in the basin to heat the cup). Place the cup with the sodium hydroxide mixture into the cold water basin---again, do not empty the cup, just place it into the water bath.

  6. 6

    Put a cooking thermometer into each cup and monitor each cup's temperature.

  7. 7

    Wait until each cup's contents reaches 50 - 55 degrees Celsius, then carefully pour the oil into the sodium hydroxide mixture.

  8. 8

    Stir the mixture with a spoon until it reaches "trace". This means that when the spoon is dragged through the mixture, it will leave a light trail behind it that lasts for several seconds.

  9. 9

    Stir in 15-20 drops vanilla essence for fragrance.

  10. 10

    Pour the soap into your chosen soap mould and allow it to harden for two to three days.

  11. 11

    Carefully remove the soap from the mould and allow it to sit in the open air for two weeks. Flip the soap over and allow it to sit for another two weeks.

  12. 12

    Use the soap as you would use any other soap, or store in cling film for later use or to give as a gift.

Tips and warnings

  • Speciality soapmaking supplies (soap moulds, fragrance oils and sodium hydroxide) can be purchased in soapmaking stores and online.
  • You can also use soap fragrance oil, honey or even powdered spices to add fragrance your soap.
  • Be careful when working with hot liquids or sodium hydroxide, as they can cause skin burns if improperly handled.

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