How to create foaming formulas - essential learning

Essential surfactants used in foaming formulas

There are 3 main classes of cleansing surfactants; a foaming formula will generally need at least 2 of these, but for better performance, foam, cleansing and wash off feeling, all 3 should be used. For more premium products and where the budget allows, two materials from the non-ionic subcategories should be included.
Watch also: 

• how surfactants are different; 
• Choosing surfactants webinar

The 3 main classes of cleansing surfactants are:

• anionic (negatively charged): 
  • anionic surfactants provide the strongest clean out of the foaming surfactants because their charge helps pull dirt and soils away from the hair and skin. Unfortunately, because they carry such a strong charge and cleansing action, their input needs to be limited and complemented by the use of at least one non-ionic surfactant or amphoteric material. 
  • common INCI names you may be familiar with include sodium lauryl sulfate, sodium lauroyl sarcosinate, sodium cocoyl isethionate, sodium cocoyl methyl taurate and sodium cocoyl glutamate. 
• amphoteric (positively charged in an acidic environment, negatively charged in an alkaline environment):
  • these materials are fantastic to boost foam and mildness in foaming formulas when paired with an anionic surfactant. 
  • common INCI names you may be familiar with include cocamidopropyl betaine or cocoamphoacetate.
• non-ionic (no net charge): 
  • non-ionic surfactants are generally to boost functionality of the foaming formula, such as boosting mildness, foam, viscosity or wash off skin feel. 
  • non-ionic surfactants can be broken down into sub-categories:
    • foamers: these boost foam, cleansing and mildness. These materials have INCI names such as coco-glucoside. 
    • solubilisers: these materials help solubilise any oil ingredients present (such as essential oils or fragrance), boost stability, improve after wash off skin feel and mildness. Common INCI names include polysorbate-20 or PEG-40 hydrogenated castor oil. 
    • superfatting: these are the main sub-category to give a beautifully soft wash off feeling to a foaming formula. Common INCI names you will see include PEG-60 almond glycerides, glyceryl oleate, sucrose cocoate or polyglyceryl-3 caprate.

How to combine surfactants for foaming formulas

A typical foaming formula will be composed of:

We say ‘active’ content, because many surfactants come as dilutions. For example, sodium lauryl sulfate may come as a 30% liquid (30% SLS, 70% water), 70% paste (70% SLS, 30% water) or >95% powder (consider it as 100% SLS). So, if we want to include 5% anionic surfactant, we would need 16.67% of a 30% active liquid; 7.14% of a 70% active paste or 5% of a >95% powder.  Each scenario still yields 5% active anionic surfactant but the liquid vs. paste vs. powder may be selected to suit processing capabilities or price. This is why when it comes to writing up formulas, you need to specify either the trade name or surfactant dilution to ensure the right materials are used when it comes to manufacturing your formula in a factory.

Watch also:

• How to formulate a basic surfactant
• Easy natural surfactant formulas

How to adjust viscosity of foaming formulas

When using an anionic surfactant with an amphoteric surfactant, this combination will often help a foaming formula thicken on its own. When you want to use all natural/naturally derived surfactants, however, it is much harder to thicken formulas. Ways to thicken foaming formulas include: 

• using an anionic and amphoteric surfactant in suitable proportions; or
• using a gum or polymer that is compatible in a foaming surfactant environment; or
• using a high HLB waxy emulsifying agent as a non-ionic superfatting material (where it is compatible with foaming surfactants) or
• adding salt to salt-responsive surfactants.

Thickening foaming formulas is quite an involved topic and will be a feature of a future blog topic. For now, here are some videos that can help get you started:

• How to thicken foaming formulas easily
• How to thicken natural surfactants without salt
• How to thicken surfactants with salt

As you can see this is just the starting point to learning how to create foaming formulas, but it should help you get underway with making the right combination of surfactant selections and better understanding why foaming formulas contain so many different types of foaming agents. 

Happy formulating!