How rheology enables better ingredient choices in personal care and detergent formulation
Formulators in personal care and fabric care face a shared challenge: products that perform well in the lab don’t always behave consistently during scale-up, storage, or real-world consumer use.
Temperature, ingredient interactions, and processing conditions can all influence how a formula behaves and performs.
Such challenges highlight why relying on visual checks or basic ingredient data alone are rarely enough.
Rheology provides a scientific foundation that empowers formulators to predict and control flow, viscosity, and structure under real-world stresses.
Producing measurable data to reduce costly setbacks
Rheology is the study of how a formulation flows and deforms under various forces.
This testing and measurement gives formulators a powerful tool to design high-performing, reliable products backed by science rather than trial and error.1
With rheology, technical teams can determine how ingredient tweaks and temperature changes affect lotion thickness or exfoliant suspension, or how detergent formulations behave under pumping, mixing, or dilution at production scale.
These insights can help bridge the gap between lab success and real-world manufacturing.
How rheology helps solve real-world formulation challenges
Even small formulation tweaks can derail product performance.
In personal care product manufacturing, adding a fragrance oil may make a shampoo too runny, while a slight emulsifier change can leave a lotion too thick. Exfoliants that appear stable in the lab may later sink during storage.2 3
For detergent manufacturers, concentrated formulas can form gels under certain concentration and temperature conditions, which are difficult to re-disperse back into solution.
These examples highlight that every formulation change alters rheology, which in turn impacts how a product feels, spreads, pours, dissolves, or suspends active ingredients.
Case study: Quantifying gel behaviour in higher mole alcohol ethoxylates for detergent manufacturers
When gel formation occurs in detergents, the consequences ripple through both production and performance.
Gels slow dissolution in wash water, block filling lines during manufacturing, and force time-consuming reformulation efforts. Gels can be a particularly difficult challenge when formulating concentrated and ultra-concentrated detergents.
Why gels form:
Gels form when surfactant molecules self-assemble into ordered structures under specific temperature and concentration conditions. At certain ranges (often between about 30-70 wt% surfactant in water), molecules organise into lamellar or hexagonal phases.
Instead of remaining flowable, the formulation thickens into a semi-solid gel that resists pumping, handling, and redispersion.
From subjective to objective:
Traditionally, manufacturers have relied on visual gel mapping to understand how alcohol ethoxylates behave across conditions and to predict where gels are likely to form. While useful, this approach is slow, subjective, and inconsistent across operators and batches. Completing a single gel map can take an entire day, and the results may still vary based on human judgment.
Digitising gel analysis:
Shell Chemicals has taken a rheology-based digital approach to gel curve analysis. As published in the Journal of Surfactants and Detergents, Shell Chemicals applied oscillatory rheometry to measure both elastic and viscous moduli to produce quantifiable gel maps that show when and where gel formation occurs.
The advantages of this approach are clear:
- Objective, reproducible data: Reduces subjectivity and provides consistency across production and surfactant grades.
- Faster data generation: Gel maps that once required a minimum of one day to produce can now be completed more quickly.
- Stronger decision-making: Enables efficient comparison of surfactant formulations and provides insight into how molecular parameters like EO number and alkyl chain length affect gel behaviour.
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Key rheological tests and what they reveal
In fabric care and personal care formulation, understanding flow and structure behaviour is essential to avoiding costly processing issues and ensuring product performance.
The table below details how specific types of rheological tests can deliver actionable insights for product formulation.4 5
| Test type | Reveals | Use case |
|---|---|---|
| Viscosity vs. shear rate | Identifies shear-thinning or shear-thickening behaviour. | Ensures shampoos, creams, and detergents stay thick in the bottle but flow easily when pumped, poured, or spread. |
| Yield stress | Measures the minimum stress needed to initiate flow, indicating whether a structured fluid will resist movement at rest. | Prevents leaks in packaging and keeps particles such as capsules or exfoliants suspended until use. |
| Oscillatory testing | Quantifies elastic and viscous behaviour to assess gel texture. | Helps formulators design detergents that stay pourable and lotions that feel structured yet smooth, while providing objective gel maps that replace subjective visual checks. |
| Thixotropy | Shows how quickly a material rebuilds thickness after being mixed, shaken, or pumped. | Ensures lotions and cosmetics rebuild viscosity after spreading so they don’t drip, run, or feel thin. |
In personal care, rheological screening is also used as a quick, consistent way to gain preliminary insight into sensory attributes such as thickness, spreadability, or texture.
While not a replacement for human sensory testing, rheology provides valuable data that complements subjective evaluation and helps avoid the blind spots from relying on viscosity alone.
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Formulate with confidence, supported by rheology and Shell NEODOL®
Many ingredient manufacturers provide viscosity data through product and technical data sheets.
Shell Chemicals goes further by tailoring rheological analysis to customer needs, offering detailed profiles and collaborative interpretation.
Our highly sensitive instruments operate across a broad temperature range and use interchangeable measuring systems to handle diverse sample types and testing scenarios, delivering relevant data beyond standard viscosity figures.
Shell NEODOL alcohol ethoxylates, relied upon by personal care and fabric care formulators alike, are tested for gel phase formation, flow, and stability, enabling teams to more confidently predict behaviour across applications.
Our team supports customers when their internal resources are limited, helping to bridge gaps with targeted data, scale-up guidance, and formulation troubleshooting.
This approach helps accelerate development, reduces reliance on trial and error, and gives formulators greater confidence from lab to scale-up.
Sources
1 https://www.tainstruments.com/how-rheology-helps-personal-care-products-meet-consumer-expectations-blog
2 https://cosmeticsbusiness.com/testing-taking-rheological-control-59936
3 https://www.tainstruments.com/pdf/literature/AAN016_V1_U_StructFluids.pdf
4 https://www.tainstruments.com/pdf/literature/AAN016_V1_U_StructFluids.pdf
5 https://wiki.anton-paar.com/en/basics-of-rheology/