When it comes to curly hair care, understanding the role of key ingredients in your products can make a world of difference. One such ingredient that often goes unnoticed but plays a pivotal role is film forming humectants.
So, what exactly are these? Film forming humectants are special compounds that not only draw moisture into your hair but also create a thin, protective layer around each strand. This layer helps to seal in that much-needed moisture, keeping your curls hydrated and healthy for longer periods. This feature is especially beneficial for curly hair, which has a natural tendency to lose moisture more quickly than straight hair due to its unique structure.
To offer further insights into the science behind these ingredients, I’ve enlisted the expertise of a friend who is a seasoned hair scientist and cosmetic formulator holding a PhD in Chemistry. His expert insights will shed light on the topic, helping us navigate the world of curly hair care with confidence.
Film Forming Humectants: The Connection to Hair Care
Water is vital for maintaining the health of your skin, scalp, and hair fiber. When there isn’t enough moisture, your hair can become dry, brittle, and rough.1,2,3 That’s why many products use the terms “Moisturizing” and “Hydrating” to market themselves and draw in customers.
Humectants are chemical compounds frequently used in hair care formulation to impart water molecules to hair fibers. These molecules can attract, bind, and retain moisture, including water molecules present in the surrounding air.
Glycerin, propylene glycol, and sorbitol are traditional and well-known humectants. But, their effectiveness mainly relies on the humidity level of the environment. In case of low humidity, where there are fewer water molecules, they might not work correctly, and this might even harm the quality of the hair.4
There are new polymeric humectants available that can replace traditional humectants. These new ones are known as film-forming humectants because they create a thin and gentle layer over the hair shaft. These are versatile, multifunctional, and most importantly, nature-derived ingredients that provide adequate water to the hair fibers.
Film-Forming Humectants: What Are They?
Film-forming humectants are a type of natural polymer that is either extracted or obtained from plants and similar natural sources. These humectants attach to the surface of hair through weak chemical bonding and create a delicate coating along the surface of the hair. This coating is thin, flexible, and does not block the flow of water.
These film-forming humectants are starch or protein-derived ingredients with a large molecular structure and high molecular weight. They are water-soluble and can attract water molecules from the air.
Polymeric materials possess unique characteristics in their molecular structure, consisting of water-binding hydroxyl groups (or, related hydrophilic groups or amino groups) that attract water molecules from the air through hydrogen bonding.
Some examples of such film-forming humectants are:
Starch-based:
● Starch, Modified Starch from Corn, Oats, Barely, etc.
● Pectin
● Aloe Vera Gel or Leaf Juice
● Guar Gum, Xanthan Gum, Gum Arabic, Locust Bean Gum
Protein-based:
● Hydrolyzed Proteins e.g. Hydrolyzed Wheat Protein, Hydrolyzed Keratin, Hydrolyzed Soy Protein, etc.
● Amino Acids e.g. Hydrolyzed Wheat Amino Acids etc.
● Collagen
How Film-Forming Humectants Differ From Traditional Humectants
Humectants like glycerin and propylene glycol are considered traditional because they are polyhydric alcohols with multiple hydroxyl groups attached to a small carbon chain. In contrast, Film-forming humectants are very different in their chemical structure and physical and chemical properties.
Glycerin or propylene glycol are small molecules that have small molecular weight whereas most of the film-forming humectants are large polymeric materials with high molecular weight.
Furthermore, their ability to attract water molecules from the air and hold them is also different from traditional humectants. Additionally, due to their starch or protein-based molecular structure, they are less affected by changes in humidity.
These particular film-forming humectants do not immediately release water molecules under dry conditions. Instead, they slowly absorb and release moisture, which means they retain water under dry conditions for a longer period compared to traditional humectants. They release water in a smart manner as needed, leading to well-balanced and long-lasting hydration of the hair fiber.
Benefits of Film Forming Humectants
● Film formation over the shaft
● Keeps hair hydrated all the time
● Maintains the hair’s water level; not too much, not too little, and keeps it balanced
● Less affected by humidity fluctuations
● Most film-forming humectants are plant sourced, sustainable, and have good biodegradation
Who Should Use Film Forming Humectants
Film-forming humectants, which are polymeric with large molecular sizes, are suitable for all hair types, regardless of ethnic background. They do not cause heaviness or a limp-down effect because their hydrophilic film over the hair shaft is water-soluble and easy to rinse off during washing.
If you have curly hair with high porosity, chemically processed or UV-damaged hair, using film-forming humectants in your daily hair care routine can significantly help. These humectants provide a constant supply of moisture to prevent dryness, brittleness, and frizziness caused by a lack of water in your hair fibers.
We recommend that every user conducts a patch test before applying the product on their entire scalp to ensure that the formulation ingredients are compatible with their hair and scalp. However, the product works well on both virgin and non-chemically treated hair fibers and offers benefits to both types of hair.
Products Containing Film-Forming Humectants
Most of the film-forming humectants listed above are water-soluble and can be easily added to hair shampoos, rinse-off conditioners, leave-in conditioners as well as deep-conditioning masks.
Being a film former, they are more effective in a formulation that is designed to stay on hair for a certain period, such as a leave-in conditioner or deep conditioning mask since it provides time for these ingredients to bind the hair surface and form a uniform film along the entire shaft.
In addition to hair care products that are meant to be left in, film-forming humectants can also be added to cleansing formulas. These ingredients provide multiple benefits to both the hair and scalp.
For example, proteins are excellent fiber-strengthening agents that enhance the mechanical strength of damaged hair fibers.5 Aloe Vera gel is known for its scalp-hydrating and healing benefits improving the quality of the scalp surface.6
Summary
Film-forming humectants are excellent solutions for hair that is dry or damaged. They work differently from traditional polyhydric humectants by creating a gentle, delicate, flexible, and even coating over the hair shaft. This layer can then hold onto water molecules, providing a consistent supply of moisture to both the hair and scalp.
These ingredients are not affected by significant changes in humidity levels, which is important to note. Additionally, most of the humectants used in the film-forming process come from plants, are sustainable, and can boost the natural and organic qualities of the formula.
References
- Feughelman, M., Natural protein fibers. J. Appl. Polym. Sci. 2002, 83 (3), 489-507. ↩︎
- Egawa, M.; Hagihara, M.; Yanai, M., Near-infrared imaging of water in human hair. Skin Research and Technology 2012, n/a-n/a. ↩︎
- Barba, C.; Méndez, S.; Martí, M.; Parra, J. L.; Coderch, L., Water content of hair and nails. Thermochimica Acta 2009, 494 (1-2), 136-140. ↩︎
- Crowther, J. M., Understanding humectant behaviour through their water‐holding properties. Int. J. Cosmet. Sci. 2021, 43 (5), 601-609. ↩︎
- Fernandes, M. M.; Lima, C. F.; Loureiro, A.; Gomes, A. C.; Cavaco-Paulo, A., Keratin-based peptide: biological evaluation and strengthening properties on relaxed hair. Inter. J. of Cosmet. Sci 2012, 34 (4), 338-346. ↩︎
- Hamman, J. H., Composition and applications of Aloe vera leaf gel. Molecules 2008, 13 (8), 1599-1616. ↩︎
