Chemistry Science Fair Projects Making Ph Neutral Soaps

Chemistry science fair projects: Making pH neutral soaps

Learning how to make pH neutral soap is an excellent, and moderately easy, project to choose for a Chemistry Science Fair Project. Before we actually delve into the process of how to actually make soap pH neutral, it will help to understand a little bit background information and history pertaining to how soap came into existence, and how the various methods of soap making have evolved through the years, to produce what we call “Soap” today.

According to, Soap is defined as: “a substance used for washing and cleansing purposes, usually made by treating a fat with an alkali, as sodium or potassium hydroxide, and consisting chiefly of the sodium or potassium salts of the acids contained in the fat.”

The process of making homemade soap has a long history. No one is exactly certain when it first appeared, but examples of what is thought to be soap have been discovered dating as far back in history as 2800 BC.  In the 8th century, soap was made using sodium alkali. Potash and pearlash, other common alkalis found in plants and wood, have also been used to make soap throughout history. Over time, however, other ingredients have come to be included in soap making, giving us a wide variety among the soaps we have to choose from today.

On a historical level, it is interesting to note that the remains of a soap making factory and several completed bars of soap were found in the ruins of Pompeii, when Mt Vesuvius erupted in 79 AD

Before learning how to make pH neutral soap, it is helpful to understand why it is desirable and even helpful to change the pH factor of soap. pH is defined as “a scale to measure the acidity or alkalinity of a chemical typically dissolved in water.” The scale is from 0, which is very acidic, to 14, which is very alkaline. Water is near the middle of this scale, with a pH of 7.

Our largest organ is the skin in which we live. It serves to perform several very important functions. It helps to protect our insides from harmful substances, and it is essential in eliminating toxins from our bodies. Our skin also helps to control the temperature of our bodies. When skin is in balance, it has a pH of somewhere between 4.5 and 6.0 The “Acid Mantle” is what provides protection for our skin. It helps to protect us from harmful bacteria. When our skin’s pH factor is too high or too low, harmful bacteria can form and grow, leading to a host of skin problems.

Now that you have a better grasp of the origins of soap, it is time to make some soap for yourself. Here is a basic recipe I found on line for making homemade soap:

Equipment required for basic soap making:

· A double boiler or a pot and lid on top of a slightly larger pan.
· Soap molds (plastic or metal – Tupperware, PVC pipe, drawer organizers, Jell-O molds, candy molds, loaf tins, etc.). You can choose which ever type of mold that you desire.
· Rubbing alcohol in a spritz bottle (removes any excess air bubbles and works as an adhesive for embedding objects or layers).
· 1lb of clear soap base 


Melt the soap block in a double boiler keeping it covered with a lid to prevent moisture loss. You can also melt the soap block in the microwave on a low setting. Avoid hot temperatures.
You can now add scents to your soap. If you have a favorite type of perfume or cologne this would be the perfect time to add a few drops, but not too many. 

This is also a perfect time to add any other additives you may want to place inside of your soap. For example: honey, oatmeal, toys (for embedding), oils etc. However, fresh or dry flowers are not recommended because they will cause the soap to become rancid and dried out. 

Now it is time to embed any objects that you wish. Once the soap block is melted – pour a thin layer of melted soap into a mold of your choice and allow it to become firm (about 5 – 10 minutes). This will allow the object you wish to embed to sit on top. Place object on top and lightly spritz with alcohol. Pour remaining soap on top. Replace any swimming objects back to desired position and allow enough time for the soap to set. 

Once you’ve added your optional ingredients if any – pour into molds. Spritz with rubbing alcohol to avoid air bubbles. Allow time to set. Ready to use once it is hard. “Melt and pour soaps” are high in glycerin which evaporates if not wrapped in plastic wrap. Make sure that you do wrap up your soap to avoid this situation.

Once you have made your soap, you will want to test the pH factor of the bars, to ensure the safety of your product.

The website offers the following pH testing method for your soap:

“You can test your soap for excess lye by applying a few drops of Phenolphthalein, a colorless, clear liquid. This chemical will turn pink or fuchsia in the presence of an alkali or an excess of lye. Soap that is to be used on the skin should be in the range of 7 to 9.5.
It’s the degree of pink that determines how alkaline your soap is. If a drop applied to the middle of a soap cutting turns deep pink or fuchsia then the soap should not be used on the skin. This soap however is great for the house or laundry.

If the drop stays clear or turns just the lightest shade of transparent pink then your soap should be fine.

If your soap was left uncovered while in the mould then the white chalk-like substance on the surface (soda ash) will also test alkaline. This can be trimmed off or avoided by applying plastic wrap to the surface right after pouring your soap into the mould.”

If the soap is too high or too low in pH, you can change the pH factor by incorporating any other the following ingredients into your next batch of soap:

Powdered Goat’s milk

Flax seed Oil (Omega-3)

Olive Oil (Omega-6 and -9)

Sunflower Oil (Omega-9)

One good indicator that soap is very close to being neutral is that it will be nearly clear, or perhaps have a light golden transparent tinge to it.

Feel free to research and experiment with other additives, which can be found through an on line search, to find other ways to change the pH of homemade soap. Be creative, but always remember to practice safety measures. Lye is a very dangerous substance. Use proper eye and skin protection.

With a little experimentation with different types of soaps, both those that are unscented, and ones with essential oils added for fragrance, you should have a fun, and interesting, Science Project to share with others.

Sources, Links, and Useful Information:

How to Test the pH Level of Homemade Soap |

How to Test the pH Level of Homemade Soap |