Thickening a Gel Formula with Cocamidopropyl Betaine
Question
I am making a gel formula using only cocamidopropyl betaine as the surfactant. I tried adding salt (electrolytes) to increase the viscosity, but it did not thicken the gel. Why doesn't adding salt work for cocamidopropyl betaine, and what are alternative methods to thicken this type of formula?
Answer
Based on the information provided, adding salt (electrolytes) is a method used to increase the viscosity of anionic surfactants like SLS or SLES. However, this method is not effective for non-ionic surfactants (such as lauryl glucoside, decyl glucoside) or amphoteric surfactants like cocamidopropyl betaine (coco betaine).
Therefore, your experience of the gel not thickening when adding salt to a formulation using only coco betaine is expected and correct.
To increase the viscosity of a formulation primarily using cocamidopropyl betaine, you can use thickeners such as xanthan gum or guar gum. After achieving the desired viscosity, adjusting the pH of the formula down to 5-6 using citric acid can help improve stability.
Mixing tip: Always dissolve the gum thickener in the water phase thoroughly before adding the surfactant to avoid excessive foaming during the mixing process.