Why does one cream feel just right while another does not? Rheology explains how texture, spreadability, and stability shape both our cosmetic preferences and a product’s performance. From sensory experience to shelf-life, this is the science behind how cosmetics feel and function.
One important aspect in cosmetics is how a certain product feels. Everyone has a different preference, and it’s important for formulations to take those preferences into consideration. Not only is sensation important, but how a product physically behaves has a huge impact on shelf-life, stability and even mode of action.
When choosing a cosmetic product, such as creams, serums, deodorants, toothpastes, soaps, etc., we all may have a strong preference for certain textures. If something feels ‘off’, whether because it feels ‘slimy’, doesn’t spread evenly, or leaves an undesirable after-feeling, this will impact our choice when deciding which brand of soap we go for. And while this preference is deeply personal, certain sensations are more universally preferred above others. Rheology is the study of the flow of matter, particularly liquids and “soft-solids”. When it comes to cosmetics, rheology studies the viscosity, spreadability and flow of the products we use, making it possible to quantify our preferences, aiding in consistent and reliable formulations.
Besides consumer preference for how a product feels, the flow of a product also plays a crucial role in its effectiveness. If the product’s goal is in improved hydration, barrier and film formation capabilities are crucial for retaining moisture, and thus the product’s flow and coverage is a key consideration. On the other hand, let’s say that the product’s selling point is an active ingredient, such as a vitamin C and salicylic acid day-serum. The homogeneous dispersion of these ingredients is important for the product’s efficiency, as well as its shelf-life, especially for sensitive ingredients such as vitamin C. A deep understanding of rheology provides a strong foundation for these considerations during formulations.
And exactly how is this insightful side of science studied? Various devices such as rheometers or viscometers employ a variety of tests to determine a materials flow and viscosity. A viscometer , without getting too complicated (which it very quickly does in this science!), measures the flow of an object, whether by dragging an object through a stationary fluid (such as rolling a ball through the gel), or by allowing the fluid to run by a stationary object (measuring the drip of a viscous liquid though a capillary tube). These are only a couple of examples of viscometers, with many other tests and machines available. And for more complex fluids, a rheometer is used to determine how a fluid flows in response to applied forces.
With all of this, Rheology can be appreciated as a complex science that offers not only concrete data for shelf-life and homogeneity, but also a quantifiable understanding of more abstract consumer preferences. Interested in quantifying the viscosity of your sample? Reach out to us for more information!
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