How to Make Olive Oil Soap and the Chemistry Behind It




Introduction: How to Make Olive Oil Soap and the Chemistry Behind It

Soap is one of those things in life that we cannot live without. From washing our hard working hands to cleaning up from some of life's greatest moments, soap has many uses. What most do not realize is that soap is actually a wonder of chemistry. Soap making is a calculated and detailed process that, if done correctly, produces hundreds of products. Soap is made as a bi-product from the chemical reaction of oils and fats.

The first written accounts of soap recipes are from 2800 BC. created by the Babylonians and Ancient Egyptians. Created for the purpose of washing dishes, the recipes were strengthened and perfected and has gone down in history as the earliest known chemical reactions used in mass production. These early soaps were used in an array of different places, including aiding in the cure for skin diseases. (

First made from animal fats, soaps are now made from a variety of oils including olive oil, coconut oil and many others. In short, the process of creating soap uses these oils in a reaction with a strong base such as sodium hydroxide.

The following is a step by step instructional on how to make soap from olive oil and the chemistry behind it.

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Step 1: Equipment Necessary

Making soap, as mentioned before, is an extremely calculated process and the equipment you use is key to producing a quality soap. Below are the tools and equipment necessary.


1. A heat source that can maintain your solution at a temperature of 45 to 54 degrees centigrade - for our soap, we used a hotplate

2. A container that can be used to heat your fat to the determined temperature and can hold your fats and where you can mix your ingredients - for our process we used a 1 liter beaker

3. A scale to weigh the amount of fats that will be used in your soap making

4. Measuring cups, beakers or other containers to measure out the other ingredients that will be used

5. A stir rod or other method to stir your solution during the process. This is a key part of making saponification happen


1. Virgin Olive Oil

2. Sodium Hydroxide in the amount needed for your specific soap recipe *Lye is extremely hazardous to the touch and should be handled with extreme care to avoid burns on skin*

3. Additional essential oils/scents

4. Molds that soap can solidify in

Step 2: Design Your Soap Recipe

A good soap recipe is key to making soap that has the proper consistency and eventually does what soap is designed to do, break down oils and help keep our lives clean. Lye, otherwise known as sodium hydroxide or potassium hydroxide, is mixed with the oils in the proper ratio to create soap. Lye during the saponification process breaks apart the triglyceride from the glycerol ions. The sodium ions then combine to form the soap molecules.


First, determine how much oil or fat you are going to use for your recipe. This all depends on how much soap you are trying to produce. For example, are you wanting to make a single bar of soap or several pounds of soap that can be used to make a few bars of soap? The type of oil/fats use choose to use in your soap are also key to the kind of soap you are wanting to make. These fatty acids molecules are chains, and the length and structure of the chain are what determine how structured or unstructured the soap is. Fatty acid chains that are long and saturated stay solid at higher temperatures as they have a stronger bond with each other. Chains that are shorter and are unsaturated, meaning that they have double carbon bonds which bend their structure, do not have as strong of bonds and therefor can be separated at lower temperatures.

Olive Oil, which is the triglyceride that we used for our soap and the rest of these instructions are designed for, it is a monounsaturated chain, meaning that it will be more soft than other oils.


The next step is to calculate how much lye is going to be needed to completely react with the fats. To do this, you have to use the saponification value of the fats you will be using per gram. This number can be found using a sap. calculator ( The sap. value is how many mg of lye it will take to react with 1g of your oil/fat.


Lye, otherwise known as sodium hydroxide or potassium hydroxide, is mixed with the oils in the proper ratio to create soap. Lye during the saponification process breaks apart the triglyceride from the glycerol ions. The sodium ions then combine to form the soap molecules.Saponification produces compounds that are called surfactants. Soap and many other emulsifying substances have non-polar hydrocarbon chains that repel water and an end that is polar. For this reason, the polar end of the molecule will dissolve leaving the non-polar end remaining. This process of dissolving in water created micelles, which are the key to making soap work. These micelles trap the grease and grime and breaks up their particles and dissolves them because both are non-polar.

Calculations to Determine Your Soap Recipe

1. Divide sap. value by the molar mass of your lye

2. Determine how many moles of lye will be needed for each mole of triglyceride. This will be the mole ratio of the reaction

3. Determine the number of moles of triglycerides in 1 gram of your fat. Divide 1g by the number of moles of triglycerides to calculate the average molar mass of your fat

4. Lye alone cannot be used to make soap and has to be combined with water. The general rule is that the amount of water used should be around 38% of the weight of your fat. This amount of water determines what your lye solution consists of. For example, our soap was made using a 6 molar solution of sodium hydroxide meaning that every liter of the solution had six moles of sodium hydroxide. You can purchase pre-mixed bottles of lye and the labeling will tell you this information.

Step 3: Measure Your Olive Oil/Heat Olive Oil

As mentioned before, each soap recipe can be different based off what kinds of fats/oils are used. Our recipe used only olive oil in order to give our soap a soft and moist consistency. With the goal of making .75 pounds of soap, we used 300ml of extra virgin olive oil.

Pour this olive oil into the beaker and place over your heat source.

Heat the olive oil to a temperature range of 120-130 degrees Fahrenheit.

It is important to keep your solution at this range for the entire soap making process.

Step 4: Measure Your Lye

Having the proper amount of lye is key to giving your soap the right consistency. Using the calculation in the picture, we determine how much lye would be the right amount to react properly with all of the oil.

*SODIUM HYDROXIDE CAN CAUSE SEVERE BURNS AND EYE DAMAGE - While using this chemical solution, use of protective gloves and eyewear is highly recommended. Avoid all contact with sodium hydroxide.*

After the olive oil has reached its' proper temperature, slowly pour the sodium hydroxide into the beaker. It is key to stir the solution during this process.

Step 5: Add Essential Oils

If desired add essential oils for scent at this point. Our soap used coconut dream oil. Soap needs to smell good so that you can smell good.

You could also add small amounts of oils over the course of this process, allowing it to get mixed in more effectively.

Step 6: Stir the Solution (Saponification Process)

Stirring your solution is very important to the saponification process. After your lye is added to the oils and it is at the proper temperature, the saponification reaction begins. Stirring ensures that the oils and the lye all come in contact with each other. Continue stirring your soap solution until it becomes thick.

Keep your solution over the heat and maintain its' temperature until it begins to bubble on top.

Step 7: Pour Soap Into Molds

After your soap has reached its bubbling and thick state, it is time to place it in a mold for it to solidify into. Keep in mind how much soap oil you started with and ensure that you have the right amount of space to hold that quantity. Remove your solution from the heat and pour into the molds.

pH Testing Your Soap

Having too much lye in your soap can be dangerous as it is extremely basic and can cause severe burns to the skin and your eyes. Using pH strips, at this point you can test your soap's pH to ensure that all lye has reacted and your soap will be safe to use. Your pH should be around neutral, or 7, on the pH scale. Any higher than that means your soap still contains unused lye and could be a danger to use.

Step 8: Allow Soap to Solidify

While the saponification process has already happened and the soap could be used right away, allowing it to solidify creates the characteristic bar of soap that can be used for everything from cleaning dishes to bath time.

24 hours is the minimum amount of time needed for the soap to solidify, however the longer the soap can be left alone, the longer it lasts.

Step 9: Clean Up

Clean up is a very important step. Since you are dealing with such toxic chemicals, it is very important that these materials are cleaned up correctly. After you are done using the graduated cylinder that contained the sodium hydroxide, pour vinegar into the container. This will neutralize the sodium hydroxide making it safe to pour down the drain. After that, test the PH and make sure it is about 7 before you pour it down the drain. Ensure that all of the equipment that you used is clean and free of sodium hydroxide before using again or putting away.

Step 10: Reflection

After allowing our soap to cure for 3 days, we cut it from its mold and used it for the first time. Our soap was just as easy and pleasant to use as the commercially available products, and in fact it smelled and felt better in your hand. Other soaps made at the same time using different products seemed to yield better results than bars of soap that can be bought from the store. Not only does it feel better in your hand but you have the satisfaction of making something yourself.

Our ratio for our soap was 100% olive oil. We used one single ingredient and that made for a very interesting final result. Other ingredients would alter your ratio of triglycerides to lye and would create a different consistency of soap.


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    6 Discussions


    Question 1 year ago on Step 8

    Hi, can I have calculation spreadsheet from How to Make Olive Oil Soap and the Chemistry Behind It please. Thanks, Alex


    1 year ago

    Hi! A friend of mine is trying to make liquid soap for the first time. I came to your site trying to find information to help her. So, I have some questions:
    - You wrote "The sap. value is how many mg of lye it will take to react with 1g of your oil/fat." Are you sure this is correct? Or was it ... "grames of lye" (instead of mg)?

    - By lye, I guess you mean KOH or NaOH, right?

    - What temperature should the mixture be on? Is 100 degrees Celsius enough (like on a water bath)?
    - What happens if (for a liquid soap recipe) one puts to much water (like 2-3 times more than needed)?


    4 years ago

    I gather that the posting were from a school project. I have read a few of the postings by the participants. Having made soap for my personal use for over 15 years from saved bacon fat, I have known that a nice hard bar of soap does not occur until the individual bars are cut and air cured over weeks. I don't test my soap with ph paper. I probably don't use the produced soap for months as I have a stock pile of prepared soap available. Cured soap often has a slight white film that was explained to me as any residual NaOh reacting with the atmospheric C02 and resulting in sodium carbonate. I love the chemical magic and the final clean aroma of a cured bar of soap.


    4 years ago

    Ooh! Where can I buy coconut dream oil?


    4 years ago

    Was this done for a school project? I see a few new soapmaking posts that also focus on the chemistry behind it.