If you compare the molecule above to that of SLS (from yesterday), you'll see that little oxygen (O) atom is messing up the clean squiggliness of the carbon chain. That's the ether part of the process. (Ethers are a type of organic molecule that contains an oxygen joining two alkyl groups. You can see how the oxygen is in the middle, implying it is connecting stuff.)
Alkyl ether sulfates - like sodium laureth sulfate (SLeS) - have good foam stability in hard water, good skin tolerance (less irritation), and are easily thickened by salt, Crothix, or glycol distearate. They are also thickened by adding cocamidopropyl betaine. It is considered a mild cleanser (definitely milder than SLS!).
You can find SLeS in two forms - SLeS 2 EO (or SLeS 2 mole) and SLeS 3 EO (or SLeS 3 mole). This EO part is about the ethoxylation of the surfactant. The higher the ethoxylation, the less irritating it will be for your skin or eyes and the more soluble in water.
You'll also find different concentrations of the amount of SLeS in your bottle. I use Stepan Steol CS-230 (click here for the data bulletin sheet for Steol CS-230), which contains 26% active SLeS and is a 2 mole version. It has a pH of 6 to 7.5 and a freezing point of -2˚C.
For SLeS, we find mild to moderate skin irritation at 10% active. So if you used 40% SLeS in your body wash, you'd get 10.4% active SLeS in your product, which could cause some mild skin irritation. You wouldn't want to use that much of one surfactant in any product, so it's safe to say that this is a less irritating surfactant than SLS and on par with most of the others we'll be investigating!
We're also seeing ammonium laureth sulfate gaining in popularity. It has all the qualities of SLeS - good foaming and stability in hard water, better skin tolerance, good thickening with salts - with a little more mildness. It is considered a gentle to mild cleanser. Stepan's Steol CA-230 is 25% active with 15% required for mild to moderate skin irritation, which means you need to use 60% before you get that to that amount! It has a pH of 6.5.
Either of these surfactants would be suitable for most, if not all, skin types. The more sensitive skin types might prefer ALeS over SLeS because of its increased mildness.
I enjoy using both SLeS and ALeS in my creations, so here are a few ideas for formulating with alkyl ether sulfates!
Join me tomorrow for more fun with the sulfates!