Surfactants for AHA cleanser

Hi fellow formulators

I'm having trouble choosing the right surfactants for a gentle AHA cleanser, pH=4.5, sulfate free.

Below is what I have tested so far;

1- 10% Sodium Cocoyl Glutamate (Plantapon ACG HC) in water
- Reducing the pH to 5.0 using Lactic Acid, completely opaque, viscosity broke, after 5 minutes sitting without mixing, turned to an opaque gel.

2- 10% Disodium Cocoamphodiacetate (Dehyton DC-AS) in water
- Reducing the pH to 5.8 using Lactic Acid, completely opaque

3- 10% Sodium Lauramphodiacetate in water
- Reducing the pH to 4.5 using Lactic Acid, clear no sediment

4- 10% Coco Glucoside or 10% Caprylyl/Capryl Glucoside in water
- Reducing the pH to 4 using Lactic Acid, they both stay clear with no sediments.

My questions are:
- What is the best Anionic surfactant (sulfate free) option for pH around 4.5?
- Why Cocoamphodiacetate is unstable at low pH while Lauramphodiacetate is stable?
- Between Coco Glucoside and Caprylyl/Capryl Glucoside, which one has a better foam and milder?
- Is there a source to compare surfactants mildness, foam and pH stability?

Thanks for reading this long post and hope to hear your thoughts.

Comments

  • What about Sodium C14-16 Olefin Sulfonate and cocoamidopropyl betaine? Here is a neat chart of sulfate free surfactants with details, off of Making Skincare https://makingskincare.com/sulfate-free-surfactants/
  • AgateAgate Member
    Can't answer all the questions, but from my experience I haven't noticed a difference between Coco Glucoside and Caprylyl/Capryl Glucoside in mildness or foam. The main difference that I've seen is that Coco Glucoside is cheaper but Capryl/Caprylyl Glucoside works better as a solubilizer.
  • StormStorm Member
    What about Sodium C14-16 Olefin Sulfonate and cocoamidopropyl betaine? Here is a neat chart of sulfate free surfactants with details, off of Making Skincare https://makingskincare.com/sulfate-free-surfactants/
    What a useful chart, thanks for sharing Melinda.
    I don't have access to small quantities of Sodium C14-16 Olefin Sulfonate but form the chart Pureact LSR (Sodium Lauroyl Sarcosinate) seems to be another option.
    Not sure if Sodium Lauroyl Sarcosinate can be used as primary surfactant though? have you worked with this one before?
  • StormStorm Member
    Agate said:
    Can't answer all the questions, but from my experience I haven't noticed a difference between Coco Glucoside and Caprylyl/Capryl Glucoside in mildness or foam. The main difference that I've seen is that Coco Glucoside is cheaper but Capryl/Caprylyl Glucoside works better as a solubilizer.
    Thanks Agate for the comment. How does Decyl Glucoside compare with the other two?
  • Pureact WS Conc-Sodium Methyl Cocoyl Taurate would be a perfect surfactant for this type of application. 
  • StormStorm Member
    chemist1 said:
    Pureact WS Conc-Sodium Methyl Cocoyl Taurate would be a perfect surfactant for this type of application. 
    Thanks for the suggestion Chemist1. I'll give it a try.
    I'm wondering at pH=4.5 do I need to include an amphoteric? Chemically speaking it will turn to a cationic at that pH right? Wondering if that will be incompatible with the rest of ingredients!
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