Article by: Perry Romanowski

Formulating cosmetics can be a challenge. You’ve got to make a product that performs well enough for your consumers, is easy to make for your manufacturer, is inexpensive enough for your purchasing department, and contains story ingredients that make your marketing people happy. 

But formulating “natural” cosmetics is even tougher. Not only do you have to satisfy all the typical things as a standard formulator, you also have to do it with a much smaller pallet of possible ingredients. Some of the best-performing ingredients like petrolatum, mineral oil, surfactants, and paraben preservatives are off limits to natural formulators.

It’s a tough job.

And it’s even tougher than you think. That’s because working with natural ingredients is much harder than working with synthetic ingredients. Let me explain why.

What’s in an ingredient

To understand the problem of working with natural ingredients, you first have to understand what goes into creating a raw material. When you learn chemistry in college you typically focus on identifying individual molecules. You learn that water is H2O or salt is NaCl. In organic chemistry, you learn about more complicated molecules like Acetone or Benzene or 1,2-n,n-diethylmetatoluamide.

This creates the erroneous impression that when you see the name of a substance that you know the chemical composition of that substance.

The reality is that you don’t. Here’s why.

More than just the ingredient

Consider a simple example like Sodium Lauryl Sulfate (SLS). If you happen to know anything about naming ingredients you can work out that SLS has the following molecular structure.

When you buy SLS from one of the many raw material suppliers it’s reasonable to have the impression that the slightly yellow liquid is mostly made up of molecules of SLS. It’s not. Typically, SLS is sold as an aqueous solution often around 30%. That means the liquid sample of SLS you hold in your hand is really 70% water molecules.

But wait, it’s more complicated than that.

SLS is an attractive food source for some microorganisms so the detergent supplier can’t just sell you a solution of SLS and water. To ensure the ingredient remains free of potentially dangerous microbes a preservative is added. Not much (maybe 0.2%) but this adds more molecules to the ingredient you thought was just SLS. The exact preservative used varies but DMDM Hydantoin is common.

So, that “simple” SLS sample really contains SLS, Water, and DMDM Hydantoin. But the complication doesn’t end there. To really understand the composition of your SLS sample, you have to know how the raw material supplier creates the SLS in the first place.

Chemical reaction complication

SLS does not exist in nature. It can be obtained through different chemical reaction pathways but typically it would go something like this.

 According to Wikipedia,

“SLS is synthesized by treating lauryl alcohol with sulfur trioxide gas, oleum, or chlorosulfuric acid to produce hydrogen lauryl sulfate. The resulting product is then neutralized through the addition of sodium hydroxide or sodium carbonate.”

In considering this chemical reaction, there are a couple of problems you might notice.

First, recall from organic chemistry that no chemical reaction goes to 100% completion. The reaction to make SLS is no exception. That means in the final product there will be some residual starting materials that remain along with the products of other chemical reactions that might have occurred alongside the main reaction. Typically, the levels of these residual materials won’t have an impact on the performance of the raw material but they can. This is why stability testing is important whenever you’re substituting one supplier’s raw material with a different supplier’s material even if they have the same name.

A second, more substantial issue is that the resulting raw material will depend heavily on the starting material used. The reaction above implies that all the starting materials are 100% pure lauryl alcohol. But this isn’t true, they are blends of multiple ingredients.

Lauryl Alcohol / Acid can be obtained from a variety of sources either from plant oils (like palm or coconut) or petroleum fractions. The reality is that you never start with 100% laruic acid. If Coconut Oil is your source for lauric acid, it is only composed of 45% lauric acid. It also contains myristic acid, palmitic acid, stearic acid, etc. And all of these ingredients can undergo a similar chemical reaction to produce materials like Sodium Myristyl Sulfate, Sodium Cetyl Sulfate, or Sodium Stearyl Sulfate. While these molecules make up a smaller portion of the final raw material than the Sodium Lauryl Sulfate, the amount of these “contaminants” is not insignificant.

Composition of a simple ingredient

Now let’s review all that is in your sample of sodium lauryl sulfate. It contains a host of molecules including but not limited to

Sodium Lauryl Sulfate
Sodium Myristyl Sulfate
Sodium Cetyl sulfate
Sodium Stearyl Sulfate
Lauric acid
Myristic acid
Stearic acid

If you include other some residual reaction materials and molecules produces by side reactions, you can see that the raw material sample can become quite complicated.

Getting closer to your desired ingredient

Of course, if you only wanted SLS you can get a lot closer than your standard sample of SLS. The manufacturer could purify the starting materials so a much lower percentage of materials other than lauric acid are present. They could also separate the end product so a much purer form of SLS results. Through successive purification steps you could get to something that is 99% or greater pure SLS. However, this isn’t done since there are limited benefits and significantly higher costs in doing it.

Controlling what you get

When you formulate with SLS to produce a consistent product, you need to use a source of SLS that is largely the same. The way to ensure consistency is to conduct tests that help you identify the chemical and physical characteristics of the material. These tests are all listed in the ingredient specification sheet. You and the supplier agree on the tests to run like pH, viscosity, color checks, IR spectrometer readings, etc. and the results of these tests are listed in the Certificate of Analysis (COA) sheet that comes with the sample. This doesn’t guarantee that your raw material will be perfect but it certainly helps.

SLS is a relatively simple ingredient and its chemistry is quite well known. While it’s composition can seem complicated, it is much less complicated than natural ingredients. And this brings us to the biggest problem with using natural ingredients.

Natural ingredients

Consider a well-studied natural ingredient like Coconut Oil. The basic composition of coconut oil has been worked out and we know it contains mostly molecules of various triglycerides. It also contains low levels of other materials like polysaccharadies, proteins, etc. The exact composition also depends on the growing conditions, the genetic makeup of the plant, and the harvesting conditions.

It is much more complicated than something like Sodium Lauryl Sulfate. While you can point to one molecule and say that is SLS, you can’t point to one molecule and say that is coconut oil. Coconut oil, and most other natural materials, are complicated blends of molecules.

This makes identifying a material like coconut oil much more complicated. It naturally leads to some questions.

What is coconut oil?

When you buy coconut oil from your supplier what are you getting? And most importantly, how do you know what you are getting?

For synthetic ingredients like SLS, you create a specification sheet. You know the molecule or molecules so you set up tests to identify everything in the sample you’re buying. This is harder for an ingredient like coconut oil because there is a range of molecules that make up any sample.

However, you can create a variety of tests to identify the range of molecules in your sample of coconut oil. This won’t identify every molecule but it can give you a good enough idea so you have a consistent supply of coconut oil.

Inconsistency of natural ingredients

Unfortunately, few natural ingredients have been as well-studied and characterized as coconut oil. And this is ultimately the problem with natural ingredients.

When you use a natural ingredient like blueberry extract you literally do not know most of the molecules that make up the ingredient. There are literally hundreds of types of molecules identified according to this analysis of blueberries. Creating a useful specification sheet for such an ingredient would be nearly impossible. What usually happens is your specification sheet will identify color, odor, % solids, and maybe an IR peak. It would be a simple matter for a supplier to create a cheaper solution that meets all of your specifications without actually putting any blueberry in the extract.

Ultimately, you have no way of consistently knowing whether you are actually using a natural raw material or not.  This is why formulating consistent, high quality natural products is harder than you might imagine.


About the Author

Perry Romanowski

Perry has been formulating cosmetic products and inventing solutions to solve consumer problems since the early 1990’s. Additionally, he has written and edited numerous articles and books, taught continuing education classes for industry scientists, and developed successful websites. His latest book is Beginning Cosmetic Chemistry 3rd Edition published by Allured.

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