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What makes a surfactant “mild”?
I’ve been reading a lot about surfactants and realised that I have no idea what “mild” actually means. I’ve used so-called mild surfactants at too high a percentage just to try and totally stripped my hands, so I’m trying to get a better understanding of this term.
I have a few theories:
1. “Mild” means that you need more to achieve the same cleansing power as a “harsher” surfactant. So for example 8% Sodium Laureth Sulphate might have the same cleansing effect as 11% Coco Glucoside (made up numbers).2. “Mild” means that the surfactant somehow has a more selective action than a “harsher” surfactant, removing different components of the lipid barrier in different proportions.
3. “Mild” means that surfactants are less likely to penetrate the skin layers deeply than “harsher” ones.Is it any of these, a bit of a mix or something different? What is the science that backs claims of “mildness”?
Would appreciate any input to get me unstuck on this. -
5 Replies
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from my experience, it’s usually used to mean “less likely to irritate the skin or significantly strip the lipid layer, at recommended usage levels” -
Agree with Bill. It’s more complicated than it looks, because some surfactants tend to be ‘draggy’ on the skin (glucosides, SLES) and if the sensorials are poor, the consumer uses more of the product, which can cause defatting. TBH, shampoo design is really difficult compared to skin creams. (YMMV)
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Thanks guys!@Belassi I didn’t know glucosides were “draggy”, but in my trials I have had issues spreading it around my hair easily, causing me to use more product to cover it all. Is that the effect you’re referring to?A year into developing one shampoo (with heavy self-imposed marketing constraints) I’m definitely realizing just how difficult it is, but I like a challenge. Chemistscorner has been tremendously helpful.
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@Agate: Yes, exactly.
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All theory 1,2,3 are applicable when its claimed mild. For ex. Soda Ash is a base with ph 11 and also glucosides with ph 11. Just increasing soda ash from 2% to 3% brings ph upto 12 but on the other side even 10% glucosides makes it 11 only. If you have a formulation with 10% glucosides, it requires only 0.1 to 0.2% acid to bring down the ph to 7 but with 3% Soda ash in the formulation it takes a lot of acid to bring the ph down to that level which clearly shows how harsh and strong soda ash is compared to glucosides.
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