Saturday, June 9, 2012

How to interpret surfactant names (updated for 2012).

Thank you for responding so quickly and enthusiastically to the question - why do you think sulfates are bad for your hair? I really find the argument that some surfactants are using on degreasing floors to be a poor argument, indeed - we use water to torture people in wars, rivers can carve out things like the Grand Canyon, and flash floods can destroy towns in second, but none of this means water is bad - and I find it interesting that people who think SLS is harsh will use soap as a shampoo (which is incredibly bad for our hair!), but I did get some great insight into the perception of surfactants.

Curly Girl notes that "There are several different types of surfactants, ranging from harsh to mild, with sulfates belonging to the class that is the most harsh." She goes on to list quite a few surfactants, including the various sulfates, including ammonium laureth sulfate (ALeS), the sulfosuccinates (like DLS mild), sodium C14-16 olefin sulfonate (which is great for greasy hair!), and sodium lauryl sulfoacetate (SLSa), all of which are known to be mild or gentle surfactants. It seems that she is including anything that has the sulf- prefix in the harsh category, which is simply not the case.

I've seen other sites do the same thing. The assumption is that if the word "sodium" is at the front of the name, it means something pretty important. And if we see sulf- in the name, it must be pretty harsh. So let's take a look at how we name surfactants! (I originally wrote this post on April 6, 2010, but I though it was time to revisit the topic!)

Alkyl sulfates are organic esters of sulfuric acid created by sulfation of a fatty alcohol chain that vary according to the number of carbons in that hydrocarbon chain. (For instance, if you were sulfating lauric acid, you'd have a carbon chain of 12 carbons. If you were sulfating oleic acid, you'd have a carbon chain of 18 carbons, and so on.)
The sodium part is the cationic or positively charged ion in this surfactant.
The lauryl part indicates which fatty acid was used to make the surfactant. In this case, it's a lauric acid (C12) fatty acid.
The sulfate part indicates it was made through the process of sulfonation, and the sulfate is the negatively charged ion in this surfactant.

Interestingly enough, people are moving to using the solid sodium cocoyl sulfate (SCS) in things like shampoo bars instead of the much milder sodium cocoyl isethionate (SCI). How is SCS different than SLS or ALS? It really isn't much different. Sure, it comes in a powder while the others are a liquid, but the cocoyl part of the name means it is derived from coconut oil. It's still a member of the sulfates family - look at the sulfate part of the name - and coconut oil contains a whole lot of lauric acid, so it could be very similar, if not the same, to SLS. 

In this case, the ammonium part is the cationic or positively charged ion.
The laur- indicates it is derived from lauric acid (C12).
The -eth part indicates that it was derived from an ethoxylated fatty alcohol as opposed to directly from the lauric acid. Alkyl ether sulfates result from the sulfation of an ethoxylated fatty alcohol. Ethoxylation is the process by which ethylene oxide is added to a fatty acid alcohol to create detergent properties in a surfactant.
And the sulfate indicates it was made through the process of sulfonation. The sulfate is the negatively charged ion. 

The sodium is the cationic or positively charged ion.
The C14-C16 indicates the type of fatty acid used in the surfactant (C14 - myristic, c16 - stearic).
The olefin indicates it is a straight chain organic molecule (click here if you are dying to learn more!) It is an unsaturated alkene, a straight chain with at least one double bond. (You might remember the whole unsaturated-double bond thing from the oils and butters.)
The sulfonate part indicates it was created through a process of sulfonation, but the sulfur is directly linked to a carbon molecule.

Sulfonates are related to, but not exactly the same as, sulfates. In a sulfate, the sulfur is linked directly to the carbon chain via an oxygen atom. In a sulfonate, the sulfur is linked directly to a carbon atom (the R in the picture). 

This happy molecule is disodium laureth sulfosuccinate (known as DLS mild) and it is a mono-ester of a sodium salt. Sulfosuccinates are generally sodium salts of alkyl esters of sulfosuccinic acid that are a result of condensation of maleic anhydride with a fatty alcohol, followed by sulfonation with sodium bisulfite (NaHSO3). In other words, they are sulfonated like the other sulfates and sultanates. The monoesters of sodium salts - like our friend DLS up there - are the most common sulfosuccinates you'll find. They are considered very mild, with good foaming and detergent properties.
The disodium means there are two sodiums, the positively charged ion. 
The laur- indicates it is derived from lauric acid (C12).
The -eth part indicates that it was derived from an ethoxylated fatty alcohol as opposed to directly from the lauric acid.
The sulfosuccinate part means is a sodium salt of an alkyl ester of sulfosuccinic acid that are a result of condensation of maleic anhydride with a fatty alcohol, followed by sulfonation with a sodium bisulphate (NaHSO3). (I'll bet you're sorry you asked that question now!)

What can we take away from all of this? The sodium part of the name may be a common thing, but it doesn't mean as much as the rest of the name - the sulfonate, the sulfate, the glucoside, the sulfosuccinate. We can have something that might have ammonium or sodium as the positively charged ion, and, in general, the ammonium is milder than the sodium version. To say that something that has the word "sodium" in it indicates badness is like saying that anything that has the word "hydrogen" in it is bad for us because drinking hydrochloric acid or hydrogen peroxide is bad for us. There are many things that contain the word "sodium" or "ammonium" that have nothing to do with bath & body ingredients - sodium chloride, or table salt, for instance - that are just fine for us. The real key is the last word, which indicates what kind of surfactant we have. 

I hope I've given you a bit more information upon which to base your decisions about ingredients you'll include in your products. I'm not going to tell you what ingredients you have to use, but I do ask that you make your decisions based on good science, not fear mongering or scare writing. Ask yourself how much information that writer has on the topic, how much of what they have written is opinion versus fact, and ask them where they found this information. (Here's where I get most of my information, if you're curious!) It's amazing how much of what we think is fact simply isn't, and we need to keep our minds open to new ideas and information that might oppose that which we think we know. The best part of making our own products is making choices based upon our personal politics, philosophy, and general feelings about ingredients. All I ask that is you are making informed choices and not spreading misinformation. (Which is kinda the point of this blog!) 


7slaper said...

tonPaw"How is SCS different than SLS or ALS? ...." .
This is my favorite part! Not even all suppliers seem to be aware of that fact.

Thanks once more for your time and efforts to keep this blog up ad running and interesting. :)

Simone said...

Hi Susan,
Just a quick question - do you find a significant difference between ALS and ALeS, enough to warrant resourcing ALeS? I have found a couple of body wash recipes that call for both products. I have substituted SLeS for the ALeS but would like to know what difference the substitution has made. If you believe it enchances the overall product can you tell me who sells it - I have checked out most of the usual suppliers but without success.
Thanks again for a great blog.

Susan Barclay-Nichols said...

Hi Simone! I've answered your question in Monday's Weekend Wonderings. The short answer - I wouldn't use ALS as it's not as mild as SLeS or ALeS.

Robert said...

Thanks for bringing up this info.

The promotion of coco sulfate vs. lauryl sulfate for mildness frustrates me. Sure, the coco sulfate is bound to be a little milder on a gram-for-gram basis, but it must not occur to people that coco sulfate contains lauryl sulfate in everything but name. Depending on the "cut" of coconut alcohol used vs. that of lauryl alcohol, "sodium cocosulfate" may be comprised 50-70% of "sodium lauryl sulfate", especially of a SLS made from a broad cut "lauryl alcohol". And the part that's different is still a very similar fatty alcohol sulfate. Yet I see people discuss these as if they were completely different materials.

Dev said...

SCS just feels nicer. The lather of and foam produce by SCS is more rich feeling opposed to SLS which is why I prefer to formulate with it. But SLS and it's counterparts are cold processable so they get used for convenience when it's required. Also the difference because ammonium and sodium is minuscule. There isn't a difference in mildness between the two. One however, is usually cheaper than the other or more accessible. One also isn't as corrosive to factory equipment during production...can you guess which one? (Sodium)