Some formulation tips for personal cleansers
Dear Valerie: I want to use a cationic guar gum in a body wash, but I don’t know which is better. We have a few coded in our lab and I don’t know how big the differences are. How to choose the right one?
-AH, MAKE DECISIONS
Dear Decisions, Decisions: Cleansing formulations can benefit significantly from a cationic guar gum. Not all gummies are created equal when it comes to molecular weight and cationicity, so choosing the right grade for your body wash is something to consider carefully.
Guar hydroxypropyltrimonium chloride is formed from guar gum, a polysaccharide mechanically extracted from the endosperm of a legume, the guar seed.1 It undergoes hydrolysis and further chemical synthesis to create varying molecular weights and become cationically charged, forming hydroxypropyltrimonium guar chloride. Varying molecular weights impact the feel of skin and hair, as well as the final specification of a formulation. Cationicity will determine how prominent the gum is on skin or hair, which impacts performance.
When looking for the right cationic guar gum, first determine which ones work best in the system you are formulating. Will your shower gel be opaque or transparent? The data sheet will indicate which system it is suitable for. Be sure to check whether or not the gum requires neutralization or has any special processing considerations. Then I would consider substantiveness. In hair care, the cationicity of quaternized guar gum is extremely important because damaged hair tends to be negatively charged. This allows positively charged guar gum to deposit on the hair, providing a conditioned feel. It can also help file other the water -insoluble ingredients, such as silicones or oils. Although skin tends to be less anionic than hair, the principle of substantivity still applies. Molecular weight will also be something to note as molecular weight plays a role in sensory properties. I don’t rely on cationic guars for thickening cleaners , as thickening is not the primary advantage they offer to the formulation. When reviewing data sheets, also research whether or not the vendor recommends an eraser primarily for skin or hair.
If the cationic guar gums in your coded inventory do not have the appropriate properties for your body wash, you may need to consider coding another that matches the attributes you are looking for. That is, unless you need to use one you already own. In this case, I recommend that you create a simple formulation where you try each gum and evaluate whether or not you like the properties offered by cationic guar gum.
Dear Valerie: Can I use disodium cacaomphodiacetate alone or is it almost always recommended to use it with other surfactants?
— SINGLE OR MIXED
Dear Single or Mingle: Any surfactant can technically be used alone, but the question would be better phrased as whether or not it should be used alone.
Disodium cocoampodiacetate is an amphoteric surfactant generally used as a secondary surfactant. This means that it is generally not used alone or at the highest level of surfactant in a formulation. Disodium cocoamphodiacetate works best as a secondary surfactant due to its exceptional mildness and contribution to foaming properties. When used in conjunction with anionic surfactants, it synergistically thickens the formula. Personally, I use disodium cocoamphodiacetate when I need higher viscosity and great flash foam with tight bubbles.
While surfactants like disodium cocomphodiacetate can be used alone (one vendor recommends using it alone in wet wipes), multiple surfactants of different chemistries are required to achieve cleanup, flash foam, foam profile, rheology formula and rinsability. I compare it to a performer who sings a melody. The song sounds fuller when backed by the subtle background vocals singing the harmony. It is very similar to how a primary surfactant is supplemented with the benefits of secondary surfactants. They give your overall formula properties it wouldn’t have if you only used the main surfactant.
Another reason disodium cocoampodiacetate is best used as a secondary surfactant is that it can aid in the solubilization of other solid surfactants, such as sodium cocoyl isethionate (SCI). SCI is notoriously difficult to solubilize and maintain solubilized. Due to its amphoteric nature, disodium cacaomphodiacetate helps improve the solubility of SCI during processing, which in turn helps prevent the precipitation of SCI during product stability.2
Of course, the quickest way to determine whether or not you should use this surfactant alone is to try it on the bench and see if you like the cleaning abilities it offers throughout the experience, from from dispensing to foaming to rinsing.
- Mudgil, Deepak et al. “Guar gum: processing, properties and food applications – A review.” Journal of Food Science and Technology vol. 51.3 (2014): 409-18. doi:10.1007/s13197-011-0522-x
- Sun, James Ziming et al. “Solubilization of sodium cocoyl isethionate.” Journal of Cosmetic Science Vol. 54.6 (2003): 559-68.
Valerie George is a cosmetic chemist, science communicator, educator, leader and a strong supporter of transparency in the beauty industry. She works on the latest hair color and hair care research and is a co-host of The Beauty Brains podcast. You can find her on Instagram at @cosmetic_chemist. Do you have a wording question you want answered? Email him at the address above.