Dear Valerie: Is there a noticeable performance difference between SLES that’s ethoxylated with 2 versus 3 moles?

—Sir Factant

Dear Sir:

Operating under the assumption you’re asking about performance a consumer would notice, and the specifications of the two surfactants are the same, the answer is no.

In my prior career, we (for some reason) had one salon shampoo that used a 3-mole SLES, while the rest of our formulas used a 2-mole SLES. To consolidate our superfluity of coded ingredients, we just swapped them out, 1:1, keeping percent activity in mind. No one noticed, and the side-by-side stabilities must have been on par as we moved forward with the change. Of course, there was concern that consumers would find the product more irritating (the higher the degree of ethoxylation, the less irritating, and we were going to less ethoxylation) but I don’t recall any complaints in this area.

I see a lot more 2-mole SLES available than 3-mole, so from a supply and pricing perspective, I would consider using 2-mole for multiple suppliers who can provide material and cost-compete. Additionally, the higher the degree of ethoxylation, the more 1,4-dioxane may be present in the final product; this impurity is strictly regulated at the state level, and plaintiff’s attorneys do test. You’ll not only want to test upon initial production, but at the end of your accelerated stability.

If you’re already using one of these surfactants and are thinking of switching to the other, there are considerations to keep in mind as good practice. Validate your formulation to ensure that pH, viscosity, stability and preservative efficacy remain the same, as the ethoxylation may play a role. If RIPT or tear-free testing was done, it may need to be reconducted, depending on which direction you’re shifting.