Making real soap at home

Handmade Soap

By Cat, May 2008, moved to it’s own page July 2018 (Photo, right, from Wikimedia Commons)

Real soap, such as what you can make at home, has many advantages over commercial “soaps” that are not soap at all, but rather are detergents made from ingredients primarily synthesized from petroleum, such as sodium lauryl sulfate (SLS). Perhaps the most important advantage to real soap is that it has antimicrobial ability (whereas detergents require the addition of synthetic antimicrobials that can be harmful, such as triclosan.

In this post, I provide instructions for making bar soap, and liquid soap from a bar.

Making Soap at Home

Bar or Liquid Soap:  Notes on Ingredients

All soap requires fats or oils, an alkali, and water. The reaction that produces soap is called ‘saponification:

  • Water provides the medium in which the reaction occurs.
  • The alkali reacts with the fats/oils to produce saponified fatty acids (soap), glycerin, and more water;
  • When the alkali mixes with water, it generates heat (but for liquid soap, you need to provide additional heat), which drives the reaction, and helps to evaporate the water.

Fragrance or essential oils can also be added as optional ingredients, after saponification is complete.

None of my recipes provided here call for soap dye or colorant, but these can certainly be added along with fragrance or essential oils, after the soap has formed.

Fats & Oils:

The choice of fats or oils is the creative part of this process.  Your choices determine the fine qualities of the soap. Castile soap is the creme de la creme of soap, made entirely from vegetable oils, with a large portion (purists demand 100%) as olive oil.  Animal fats can also be used to make soap, but then it is not castile.

Your choice of specific oils, such as olive vs coconut, as well as the type of alkali used, will make a difference in the amount of alkali needed (This is a chemistry thing, and depends on the average molecular weight of the specific fat and the alkali). There are two different alkali substances used in soap-making, depending on the end-product desired; see ‘Alkali’ below for details.  It’s important to determine the correct amount of alkali, because if you use too much, some alkali will remain in your soap, making it caustic (could cause burns on your skin, or holes in your laundry).

Most recipes add at least 5% more fat than needed for the amount of alkali; this is called ‘superfatting.’  It has two benefits:

  1. Ensures that ALL the alkali will react so that none remains in your soap; and
  2. Allows you to express the properties of a particular oil (such as the moisturizing shea butter) in the soap.

You have the choice of adding the extra fat:

  • At the beginning, which then expresses the properties of all fats used in the final product; or
  • After the reaction is complete (but before the soap solidifies), to express only the properties of the added fat.


While there are other alkalis that could be used, for home recipes:

  • Bar soap requires sodium hydroxide (NaOH, or lye), and
  • Liquid soap requires potassium hydroxide (KOH, or potash).

Because lye is a major ingredient in the manufacture of methamphetamine, commercial drain-cleaning lyes such as Red Devil no longer use real lye in their formulas.  These commercial lyes WILL NOT WORK for making soap.  Therefore you have to scout around for real lye; several sources are available on the internet; you may also be able to purchase it from a local pharmacy.

Several calculators for determining the amount of alkali are available on the web, if you don’t want to go to the trouble of converting ounces to grams (and back again) and doing the reaction math. Summer Bee Meadow (6) provides a simple calculator.  Check out Candle and Soap by David Fisher (3) for other calculators.

Important Note:  Lye and potash are highly caustic and may cause serious burns.  Please read the safety precautions included with each recipe (in the pdf file) very carefully.


It is important to use distilled water, because certain minerals in tap water (such as calcium or magnesium) can form insoluble salts with the soap (soap scum), which will then precipitate out (think bath tub ring).

For more detail on making soap at home

See the following pdf files on The EssentiaList (for which I am the editor) for lots more info:

Additionally, The Basics of Soapmaking (3 pages) is the pdf of this article.

Making Liquid Soap from a Solid Bar

Making your own bars of soap can be daunting, and dangerous.  But soap making is a popular cottage industry, so likely someone in your community makes bar soaps you can buy, for making a liquid version.  This recipe is from Associated (5).

  • 1 cup firmly packed grated Castile or other bar soap soap (about two 4 oz. bars)
  • 4 cups water
  • 2 tablespoons vegetable glycerin
  1. Before you begin, grate the castile soap with a cheese grater, into a large pot. Try to shred it as fine as possible since it will take less time to melt the soap down if the pieces are small.
  2. Mix water with grated castile soap in pot. Set over low heat, stirring occasionally until soap has dissolved.
  3. Add glycerin. Keep your eye on it!
  4. Once dissolved, transfer to a jar and cover tightly.
  5. This makes a thick liquid soap. For a thinner liquid soap, add more water until desired consistency is reached.

This liquid soap has many uses (5):

  • laundry detergent
  • shower soap
  • baby soap
  • bubble bath (use as is, with added essential oil, or add up to 2 oz coconut oil)
  • shampoo (use as is, or blend ½ cup liquid Castile, 1 egg, and 1 tsp each olive oil and lemon juice in a blender; keeps 1 day in refrigerator.  Follow shampooing with a vinegar rinse:  ¼ cup vinegar in 2 quarts warm water to restore hair’s acid mantle.)


  3. (see recipes 1, 2, 3, & 4)

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