Science Corner
One of our main goals here at Science Suds is to teach you about soap and the chemistry behind soap-making! We hope we can dispel some chemistry myths and help you to better understand the products you put on your body.
What is soap, anyway?
The traditional process of soap making, at its most basic, involves combining oils, water, and lye (sodium hydroxide, more on that later!). When mixed together, a special kind of chemical reaction called saponification occurs. Essentially, this just means that the lye transforms the oils into soap!
Many big name-brand soaps go a step further to add synthetic detergents to their bars. This is not part of the traditional soap making process, and is not something we do here at Science Suds.
Wait, LYE?! Isn’t that a dangerous chemical?
Lye is an extremely caustic substance, and you definitely don’t want it on your skin! So why is it used in soap making? It’s actually not possible to make real soap without using lye!
One of the very cool parts about chemistry (in my opinion), is that the products of chemical reactions can have completely different properties from the substances that reacted together in the first place. The example I always like to use in my chemistry class is the reaction between sodium and chlorine. Sodium is a soft metal, and if you expose it to water, it will catch fire or even explode! Chlorine is a highly toxic gas that can damage your eyes and lungs. However, when sodium and chlorine react together (2Na + Cl₂ -> 2NaCl), they form a substance called sodium chloride…commonly known as table salt! Salt is not an explosive metal OR a toxic gas…it’s an edible mineral that makes our french fries taste great! Similarly, the products of the saponification reaction are not greasy like the starting oils, nor are they incredibly caustic like the lye. Instead, they are something totally new: SOAP!
That explains the lye, but what’s with the oils?
One of the most common questions new soap makers ask is if soap can be made with just one kind of oil. That fits our definition of “soap”, so why waste time using several different oils? Well, that’s where some of the artistry of soap-making comes into play.
The oils we use in soap making are made up of some substances called fatty acids. Different oils are made up of different fatty acids in different proportions. For example, olive oil is made up of primarily oleic acid, with smaller amounts of palmitic acid and linoleic acid. Coconut oil on the other hand, is made up of mainly lauric acid, with smaller amounts of myristic acid and palmitic acid. Every oil is unique in the exact proportions of these fatty acids.
Each of those fatty acids contributes different properties to the soap. Things like cleansing ability, creaminess, lather, and hardness of the bar are determined by the proportions of these fatty acids. The chart to the left shows the fatty acid profile that we like to use in our soap, and we use a combination of different oils to reach that perfect blend.