Introduction: How to Make Bar Soap

Instructable made by Skylar Smith, Grant Gibson, and Sean Thornton

Step 1: Pick Your Ingredients

The first step to making soap is picking your ingredients, typically coming from common fats and oils. We used three different ingredients for our soap. We used Walmart GV shortening and sodium hydroxide (which are the basic soap ingredients that were provided for us), and Coconut oil, an essential oil.

Step 2: Adjuncts/Aggregates

Adjuncts are ingredients that help complement the other. The adjunct that we used for our soap recipe was Coconut oil, which is an essential oil. This added more cleanliness and bubbles to the soap. It also provided more conditioning to the soap while also making the final product more firm and stable. You want to pick an aggregate that will help complement the other ingredients. An easy way to calculate your soap qualities from your ingredients is pulling up an online Soap Calculator. I recommend the SoapCalc Lye Calculator which tells you the qualities of your soap. These qualities consist of things such as hardness, cleanliness, conditioning, bubbliness, amount of iodine, etc.

Step 3: Calculate the Saponification Value

Next, you want to calculate your saponification values so you know how much of the sodium hydroxide mixture to add to your soap recipe.

An example of this calculation process is below:

Total grams x sap value = Grams NaOH
340.2 g x .141 = 47.96 g NaOH Grams NaOH x (1 mole/40 grams) - Moles of NaOH 47.96 g x (1 mol/40g) = 1.199 mol NaOH Moles NaOH x (1 liter/10.3 mole NaOH) = Liters of 10.3 mole solution 1.199 mol NaOH x (1 L/10.3 mol) = 0.116 liters (116 mL) of 10.3 mole solution

Step 4: Recognize Hazards of Potassium and Sodium Hydroxide

Sodium hydroxide is very acidic, and it will burn your skin if it come in contact with it. So, to make sure this doesn’t happen, we wear gloves, and handle the open container with caution. When measuring the sodium hydroxide using an 100 mL graduated cylinder, you must properly clean it out when you are done. Pour vinegar into the cylinder to neutralize the chemical, then dispose the vinegar into a sink, and wash the graduated cylinder out with distilled water.

Step 5: Obtain All the Equipment Required

For this lab you should obtain the following equipment:

Gloves, 1000 mL beaker and 250 mL beaker, 100 mL graduated cylinder, magnetic stir bar, thermometer, hot plate, stir rod, pH strips, soap mold, sodium hydroxide, your ingredients (For example: Walmart GV Shortening and Coconut oil).

Step 6: Measure Your Ingredients

We decided to use 70% Walmart GV shortening and 30% Coconut oil, but you should come up with your own recipe. We used a soap calculator online to calculate how many grams of the Walmart GV shortening we needed and how many grams of Coconut oil we needed. We chose a total of .75 pounds (340.3 g) for our total mass, so we used 0.225 pounds (102.05 g) of Coconut oil and we used .525 pounds (238.13 g) of Walmart GV shortening. Then we calculated how much sodium hydroxide by using the calculation process from step 3. We used 116 mL of sodium hydroxide.

Step 7: Adding the Ingredients

First, you place your fats and oils into the 1000 mL beaker and melt it. After it melts into a liquid, take the sodium hydroxide (your base) and add it to the solution slowly, then continuously mix it using the magnetic stir bar and the stir stick. Once all the sodium hydroxide is in your soap solution you want to continuously mix it until is gets thick. It should be thick enough to where you can draw a figure eight with solution using the stir stick on top of it and it should stay there for a few seconds.

Step 8: Mix the Ingredients

The heat will melt down the fats into liquid form so that they can solidify with the coconut oil. The solidification process of the soap solution takes quite a while. You want to make sure to mix the ingredients thoroughly, so they solidify in mixed form, not in two separate layers.

Step 9: Maintain the Temperature

When heating the soap solution you need to keep the temperature between 49-54 degrees Celsius. The heat helps solidify the solution faster, but you don’t want to overheat it or else it will stay in its liquid form.

Step 10: Molding the Soap and Testing the PH

Once the soap gets to the stage to where you can take your stir stick and draw a figure eight on the top of your substance then you can pour it into your mold. After you pour it into your mold you will have to let it sit for a while. Sometimes a couple of days, or more! Our soap has been sitting in its mold for a week and the bottom part of the mold is hard, but the top half is still mushy. Once the soap is solid you can use a small pH strip piece to check the pH so you know whether it is safe to use your soap or not.

Step 11: Clean Up

Once the lab has been completed, you should clean up your lab equipment. You want to take your beakers and thoroughly clean them with soap (a little ironic that you have to clean out the thing you used to make soap with soap). Then you want to make sure you put all your lab equipment away back in the place where it belongs.

Step 12: Understand the Key Concepts

Below are some of the key concepts you should take away from doing this lab. Some may be a review and others may not. All of these concepts will help you get a better understanding of what exactly you are doing in the saponification process and what reactions are taking place.

  • Fats and oils are most commonly used in the soap making process. They are most commonly used because they have 3 fatty acid chains and a glycerol (backbone) molecule. This makes an amphiphilic molecule which means has a polar and non-polar head. These competing heads of the molecule give soap a unique feature. When dissolved in water, these molecules form micelles, which are spherical aggregates. This process can also be referred to as emulsifying action, which is the ability to maintain a stable mixture with both polar and non-polar molecules. Also, salts can affect the saturated chain by increasing the hardness of the soap and making it more insoluble. The chain length can also affect the solubility. But, any combinations of oils and fats when making soap will lead to the ability to control the fatty acid mix, which is essential in making a successful soap product.
  • Adjuncts are things that are added to something else to complement to final product. An example of an important adjunct in the soap making process would be canola oil. If you are making soap entirely out of a hard substance, canola oil, a softer oil, will help compliment the final product, making soap that has the right balance of hardness to it.
  • Saponification value is represented by the milligrams of potassium hydroxide it takes to saponify (turn into soap) one gram of fat. If there is too much sodium or potassium hydroxide in soap, it can cause irritation and sometimes even burning to the skin. This is because the glycerin in the soap is bonding with the moisture in the air and then to your skin.
  • If too much oil or fat is left unsaponified, then the soap will go rancid and be too soft. This is also known as superfatting. Superfatting is allowing a certain percentage of your oils and/or fats in the soap recipe to unsaponified by deducting a percentage of the lye.
  • Lye, or sodium hydroxide has a significant role in the process of saponification. It increases the rate at which the triglyceride ester bonds divide. Once the fat molecule is broken up into the fatty acids and glycerols, and then stable at a desired temperature, you may begin mixing the substance and creating the soap.
  • The saponification process is used for fabricating soap. Soap is a very important molecule used for cleaning numerous things. Soap is an amphiphilic molecule, meaning that is has a polar head and a non-polar tail.
  • Again, the saponification process is the process of making soap. The four molecules that are involved in this chemical reaction are 3 fatty acid chains, and a glyceride. This molecule is also known as a triglyceride. Typically lye, the base, is added to the oils and/or fats to speed up the reaction. When you have melted your oils and fats to liquid form you can start to mix it with your base. Slowly, the mixture will begin reacting as you continuously stir. In the reaction, the triglyceride(s) will begin dividing, and the fatty acids will start bonding with the hydroxide ions in the base (lye) to form soap.
  • PH measures how basic or acidic a substance is by evaluating the molar concentration of hydrogen ions. If the soap is too basic (>10) , it could cause damage to the skin. If it is too acidic (<7) it could also be bad. The right balance of pH should be between 7 and 10.

Step 13: Our Reflection

I have not had the chance to test our soap due to it not being in my possession, but if it were I have a feeling it would be very rough on the skin and a very hard soap because of the ingredients that were used to make it. While our soap would probably be rough and hard, commercial products are soothing and soft and you enjoy putting most of the commercial soaps on your hands.

We used a simple combination of coconut oil and vegetable shortening in a ratio of 4:1, this affected our final outcome by making our soap, as I speculated before, hard and rough. I think that if we had gone with our original idea and I had brought the canola oil that I was told to bring, our soap may have turned out more soft and soothing to the skin.

I think most groups got the same results that we came upon, that is, a rough hard soap that we will probably not use. On the other hand, some groups may have created a soap that they will divide into their houses and use in their everyday life. Those few are however, not us, I will probably not use our soap other than to test its quality. The differences that would have changed based on the group's final products above most likely had to do with adding more, or different ingredients than other groups did and using different ratios of the ingredients.