Chemistry Class: Stearic Acid (An Introduction)

Molecule of Stearic Acid

In today's Chemistry Class we will be talking about stearic acid. Many time i get questions on what certain ingredient is and why its use etc so I've decided to update the chemistry of all these ingredients frequently on this blog:-) I hope you readers enjoy this particular section. I know chemistry is boring, but you need to know what you are using and why to produce a quality product and thats why I'm here to guide you:-)
So anyways back to stearic acid if you have not come across it before; This is one of the ingredient we used in our Lotion making tutorial here.



So what is it?
Stearic acid is a long chain fatty acid that contains 18 carbon molecules. Its an emulsifier where it has a water loving head (hydrophilic from the carboxylic group) , and a water hating-oil loving tail (Hydrophobic).
Now because it has both this structure, it basically can mix oil and water together hence it can be called an 'emulsifier'. However, it is not such a strong emulsifier so its usually used with another emulsifier to make cream or lotions and stearic acid are generally used to thicken the product. It is also added to soap at times to create a harder bar of soap (typically used at rate of 2%)

There are many sources of stearic acid; animal fats and plant fats. Since soaplab is vegan, our stearic acid are vegetable based stearic acid that is derived from Palm Oil.

Solubility:
Stearic Acid comes in flake form therefore it needs to be diluted with something before being used. Though its slightly soluble in water, its the best in oil. To make it soluble, heat up oil phase and stearic acid up to 70 degrees celsius to melt it. Mix all your phases (oil and water) at this temperature before cooling.

How much do we use in our product:
You can use up to 5% in your lotion or bath products. However, it tends to make the cream/ lotion very thick and feels 'waxier'. It also feels like a 'drag' when applying to skin. To avoid that i tend to use them at 2% or 3% at the max.

Application:
Its best to be used in thick creams. I personally like to use it on thick area of my body and when i want the body product i use to 'stay' on the skin rather than being absorb. So i usually make foot cream, or elbow cream using stearic acid.

Till next time.. The next chemistry class ill talk about another 'thickener' that we can use for more glider effect. till then Take care!!

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If you are one of those who wants to understand why certain ingredients is in your skincare/cosmetics, learn how to make and formulate your own cosmetic line, do contact us for our next workshop.