Surfactants for Low pH Liquid Soap with Glycolic Acid

Regarding your question about suitable primary or secondary surfactants for a liquid soap formulation containing glycolic acid at a pH of 4-5, considering foam and cleaning ability:

Based on the previous discussion:

• Clarify-Wash (Sodium C14-16 Olefin Sulfonate) provides good cleaning performance and abundant foam. However, it has a high pH (8-9), meaning you would need to use a significant amount of acid (like citric or lactic acid) to lower the formula's pH to 4-5, which could increase costs.
• SulFoam (Disodium Laureth Sulfosuccinate) and BabyFoam (Sodium Cocoyl Isethionate) have a lower pH (5-6), closer to your target pH of 4-5, which would require less acid adjustment. They are described as providing good foam, but the foam is finer and creamier compared to Clarify-Wash. Their cleaning power is noted as being less than Clarify-Wash.

The choice between these surfactants depends on your formulation priorities. If strong cleaning is paramount, Clarify-Wash might be considered, but be prepared for the pH adjustment needed. If minimizing acid use for pH adjustment and preferring a fine foam is more important, SulFoam or BabyFoam could be more suitable, potentially used in combination with other surfactants (like your existing SLES/Coco Betaine) to ensure sufficient cleaning.

Regarding the effect of oils on foam: Adding oils such as Rosehip oil or Jojoba oil to your formula will generally reduce the amount of foam produced. To counteract this and increase foam, incorporating a good foaming surfactant is necessary. SulFoam and BabyFoam are noted for their good foaming properties.

Regarding specific usage percentages and cost comparison: Recommended usage percentages for these surfactants in your specific type of formula and a direct cost comparison between Clarify-Wash, SulFoam, and BabyFoam are not available from the provided information.

Regarding compatibility with AHA (Glycolic Acid) and viscosity: Information on how SulFoam or BabyFoam specifically affect the viscosity of a formula when combined with glycolic acid at a low pH (4-5) is not available from the previous conversation. Your observation that AHA can cause some surfactant bases to become thin is a valid point and a common challenge in formulation. You would likely need to perform testing with your specific formula and chosen surfactant(s) to determine the optimal concentration and assess the stability of the viscosity.

In summary, while SulFoam or BabyFoam might be easier to work with for achieving a low pH due to their starting pH, their impact on viscosity when combined with glycolic acid is unknown and would require testing. Clarify-Wash offers strong cleaning and foam but requires more significant pH adjustment. Testing different surfactants and concentrations in your specific base formula is recommended to achieve the desired balance of foam, cleaning, pH, and viscosity.