How to Make Soap
Safety First
Materials Needed
Making Lye
Rendering Fat
Soap Making
Possible Additives


   Soap gets rid of some of the germs and bacteria that may cause diseases and it makes things look/smell better and allows them to be reused with out contamination.   

What is soap?
Soap is made of lye (a liquid solution of potash) and waste fats.  It takes three main steps:
1.     Making the Lye
2.     Rendering the Fat
3.    Mixing the lye and fat together and boiling the mixture.  (Actually the soap making step)     

Soap is not found in nature; but it can be created by a very simple process called saponification.  Saponification is the process that takes place when a fatty acid comes in contact with an alkali.  When fats or oils, which contain fatty acids are mixed with a strong alkali, the alkali first splits the fats or oils into their two major parts: fatty acids and glycerin. After this splitting of the fats or oils, the sodium or potassium part of the alkali joins with the fatty acid part of the fat or oils. This combination is called soap or the potassium or sodium salt of the fatty acid.

This web page is designed teach you how to make soap in a rural setting.   We attempted to make soap, in our kitchen using bacon grease and lye (bought from the store) and there were a few problems (described in the troubleshooting section) and since we did not have time to troubleshoot our process it was unsuccessful.  The production of safe soap will take time and experience, believe me- we are not even there yet.  We would recommend making soap with small quantities until you get the method completely right so as not to waste materials and money. 

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Safety First

-Lye (also known as sodium hydroxide)  is a caustic, alkaline substance and should not be allowed contact with the skin,  eyes etc.  because it can be harmful. This is why if the soap isn't made correctly it can 'burn' your skin.

-Do not use aluminum or tin with the lye because the lye will corrode these metals.

-Wear rubber gloves, appropriate clothing and eye protection.

-Do not stand directly over boiling mixtures and do not breathe the fumes.

- The soap should not burn skin, discontinue use if this happens.  -
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Materials Needed (besides the lye and 'clean' fat)

2-Bowls or buckets to hold fat and lye seperately-Glass or stainless steel
Food or postage scale (w/ounces wt.)
Mold for the soap to cool in
2-thermometers (candy thermometers work well, they must go up to at least 54.4 Celsius)
Salt -any salt which can be used for food
Clean cloths or rags (for filtering)
Clean cloths or rags (for insulation)
Spoon (stainless steel/ wood)
Drying rack (to cure soap)
Knife (to cut soap)
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Making Lye

-Lye (liquid solution of potash), is the liquid made when water is run through wood ashes.  We will not go through this process.  A detailed explanation of this process  can be found at ...(Brock and Cory's webpage).  If available lye can be bought in the grocery store's cleaning section.  It is called Red Devil Lye and is used for drain opening.    More about lye.

lye water
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Rendering the Fat

-Rendering fat is a process that removes the impurities in the fat.  It is the smelliest part of soap making and should be done outside for this reason.  If there are large solid chunks of debris in the fat liquid first filter it though an clean cloth or rag.

What types of fat can be used?

Animal fat, removed from the animal during butchering, or grease saved from cooking fires can be used.  These can be used if not refrigerated over a period of time, but may become rancid.  If this happens the soap may not have a pleasant smell but works just as well.  Essential oils or plant extracts may help this.
Using bacon grease


-There are a few different approaches mentioned in the links and references, both are listed below.

         First method:

  1. Place the fat/grease in a large kettle and add an equal amount of water.  Note this amount.
  2. Boil over a open fire until all the fat has melted.
  3. Continue boiling to ensure complete melting of the fat.
  4. Put the fire out and add an amount of water equal to the first.
  5. Leave overnight to allow the clean fat to solidify on the top.  All the impurities being heavier remain in the water below the layer of clean fat on the top.
  6. Remove the clean layer of fat and save for the soap making process.

Second method:

  1. Any fat is  first melted into a liquid grease.  Chop the fat into small cubes and place in a cast iron frying pan or a shallow pot.  Place over low heat until melted into a liquid.  Strain through a clean cloth to remove any large solid particles.  One pound (450 grams) of fat yields about 1 cup of grease.
  2. Place the grease in a large kettle and add an equal amount of water.  Note this amount. 
  3. Boil over a open fire.  Do not leave unattended.
  4. Put the fire out and add an amount of cold water equal to one fourth that of the first.
  5. Leave overnight to allow the clean fat to solidify on the top.  All the impurities being heavier remain in the water below the layer of clean fat on the top.
  6. When the fat has hardened scrap off the cleaner fat.  If this stills is dirty repeat steps 2-5. 
  7. On the last washing use twice as much water as fat in step 2 and add one tablespoon of salt before boiling.

Note:  If using cooking grease or rancid fat the soap product may be smelly. To fix this add four tablespoons of vinegar or lemon juice for every cup of water and cup of 'smelly' fat (two cups of total water/fat mixture) in step 2.  Another method is for each cup of melted fat add one cup of sour milk during step 1 of method 2.  Yet another method is to add a cooking potato or rice to the liquid fat in step 1 of method 2.
If using a discolored fat potassium permanganate will help to 'clean' it.  Potassium permanganate is a purple color and is sometimes called Kondies Crystals.

Washed fat can be saved in a cool airy place for a few weeks if needed before being made into soap.
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Soap Making

-Now that you know about the two ingredients necessary for making soap from scratch, lets make soap!

There are two ways soap is made: the "cold" process method, and the "hot" process method. We will briefly discuss the hot process method. However, this page is intended to explore the cold process method.  After the lye and the fats are prepared, for both processes the amount of lye can be determined from the links below.   Soap making should be done outdoors and protective gear should be worn.

Hot Process Method

The hot process method involves more heat than the cold process method.  The predetermined amount of lye and fat and set to boil.  The mixture should boil until the soap is formed. Boiling may take six to eight hours depending on the amount of the mixture and the strength of the lye. Soap is formed when the mixture becomes a thick foamy mass.  See Traditional Soap making link below for more details on this method.

Cold Process Method

The cold process method is not really heat free. Heat is used at the beginning of the process to melt the fat. 

  1. Gather and measure all the ingredients. (Remember, measurements are by weight.)
  2. Heat water over fire to a boil.  Remove water from fire and place the pot of rendered fat in the pot of water.  The idea here is to use the water melt the fat and not to mix the two.  (Temperatures should be between 32.2C and 54.4C).
  3. Heat the lye water.  (Temperature should be between 32.2C and 54.4C).
  4. When the temperatures of both are between 32.2C and 54.4C, remove both from heat.
  5. Slowly add lye to melted fat, stirring slowly and carefully.
  6. Add salt at this point if using a lye made from wood ash  if hard soap is desired.  Otherwise tracing will not occur.
  7. Continue to stir.  Do not leave mixture unattended.  Soap should trace in 15 to 30 minutes.   Tracing is when a line can be drawn in the soap mixture.
  8. Once trace is achieved, pour soap into mold.
  9. Insulate by covering with an old towel or blanket for 24 hours.
  10. Remove and cut into bars. Use gloves.
  11. Place the soap on drying racks and cure for 4-6 weeks.  Only then should the soap be used. 

lye to fatPouring

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Possible Additives
      See Traditional Soap Making link below for additives.
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Links and References
         Colonial Soap Making
         Traditional Soap Making
         A good Lye to Fat ratio table: Soap Making

         A Lye to Fat ratio calculator that uses ounces (1 ounce = 0.02835 kilogram)(warning: takes time to load): Lye to Oil Calculator
         Maria Given Nerius.  Soap making for Fun and Profit.  Prima Publishing.  1999  

How not to make soap (pitfalls to avoid)

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Created by Milagros Jean-Charles: and Amber Buhl: 
Page Created April 6, 2004
Page Updated April 28, 2004


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