Tides and stock markets ebb and flow; relationships, too. Rheology is a fact of life and a fact of cosmetic chemistry.

The New York Chapter of the Society of Cosmetic Chemists (NYSCC) recently held a one-day symposium dedicated to rheology. Speakers explained rheology basics, powder rheology, regulations and more. The event chair was Elizabeth Kaufman PhD, BYK USA.

Cindy Sullivan of Lubrizol provided insights on the regulatory landscape. She started with an overview of REACh (Registration, Evaluation, Authorization and Restriction of Chemicals). This far-reaching European Union regulation is designed to improve the protection of human health and the environment from the risks that can be posed by chemicals, while enhancing the competitiveness of the EU chemicals industry. As it pertains to cosmetics, REACh manages environmental risks of chemical ingredients. Human safety is overseen by EU cosmetic regulation.

REACh Obligations for Cosmetic Manufacturers

“Domestic manufacturers, importers and formulators must register substances and ensure compliance under REACh as downstream users,” explained Sullivan. “REACh enforces safety standards that drive innovation and competitiveness while protecting consumers and the environment.”

Substances produced over one tonne a year must be registered with detailed toxicology and risk data submitted to ECHA (the European Chemical Agency). Companies must evaluate risks and communicate safety measures throughout the supply chain to ensure proper handling. Use of substances of very high concern (SVHC) require specific authorization before incorporation into products. Sullivan reminded Symposium attendees that non-compliance can lead to fines, product reformulation or market withdrawal to maintain safety and environmental standards.

She detailed a microparticles phase-out timeline in cosmetics. Regulation EU 2023/2055 enforces phased bans on microparticles across cosmetic product categories between 2023 and 2035. By product category, exfoliating beads were banned in 2023; microparticles in rinse-off products banned by 2027; waxes and fragrances by 2029; and lip and makeup by 2035. Furthermore, packaging must indicate the presence of microparticles and provide disposable instructions to support environmental safety and awareness.

Microparticle Strategies

Sullivan noted that certain biodegradable and natural polymers, and industrial-use polymers with containment, are exempt from restrictions. She advised attendees to consider reformulation strategies such as use of biodegradable alternatives, water soluble polymers and liquid polymers.

“Consider use of derogations,” she advised. “These materials are modified where they lose their microparticle characteristics.”

But whatever strategies cosmetic chemists employ, companies must clearly label products with micro particle content, and include instructions for use to support consumer awareness and regulatory compliance.

“Synthetics are not automatically banned,” Sullivan concluded. “Work with your suppliers to understand if your material can be used.”

Natural v. Synthetic Rheology Modifiers

Sullivan’s closing statement dovetailed with a presentation by Maureen Zettel, senior formulation manager, NOAM, Lucas Meyer Cosmetics by Clariant. She reviewed the benefits of rheology modifiers:

• Textures. Serum, gel-jelly, cream, balm, gel-cream, oil, spray, lotion.

• Skin feel/sensory attributes. Spreadability, greasiness, tackiness, fluidity, absorption, coding effect, etc.

• Stability and shelf life of products. Suspension control, reduce phase separation, prevent syneresis.

• Choice. Natural, synthetic and modified biopolymer.

“Studies have found that sensory stimuli can positively influence brand perception,” said Zettel. “Textures can influence emotions, both negatively and positively. Touch is important to give a full experience of product.”

Synthetic polymers dominate with more than 60% market share, although there’s been a slight decrease in synthetic’s share from 2020 to 2024, according to Zettel. Natural polymers control more than 20%, with steady gains during the period. Demand for modified biopolymers remain the same.

Polymers and Benefits

She reviewed various polymers and their benefits. Acrylate polymers impart a quick break effect and fast absorption. They are non-greasy, but can be tacky. Examples include Carbomer, Sodium Polyacrylate and Acrylates/C10-30 Allkyl Acrylate Crosspolymer. AMPS (Acrylamido-2-methylpropanesulfonic acid) are pre-neutralized, easy to use and stable over a wide pH range. They are efficient thickeners, stabilizers and texturizers. They impart a light, fresh, silky, smooth feel on skin. Examples include Ammonium Acryloyldimethyltaurate/VP Copolymer and Sodium Polyacrylodimethyl Taurate.

Xanthan gum has a polysaccharide structure. This anionic biopolymer imparts high spreadability, but uneven flowability. It can be stringy and present some pilling. Galactomannans have a polysaccharide structure. These nonionic biopolymers include locust bean gum and tara gum. Galactomannans have a shiny and even appearance with shape memory effect, even flow behavior, easy pickup, low stringiness and nice spreadability, according to Zettel.

She reviewed three carrageenans (Kappa, Iota and Lambda). These marine-based polysaccharides impart different formulation and skin feel attributes. Kappa creates strong, rigid and brittle gels with high water retention, leading to firm texture and feels substantial to skin. Iota creates soft, flexible and elastic gels with F/T stability and less syneresis. It imparts a silky and soft skin feel, and is synergistic with Xanthan.

Finally, modified biopolymers are cellulose derivatives. They include Carboxymethyl Cellulose (CMC), Hydroxypropyl Cellulose (HPC), Methylcellulose (MC) and Cellulose Acetate (CA). In formulations, they impart a wide range of viscosities, from thin and pourable to thick and spreadable. All have shear-thinning behavior. They impart a smooth, light, non-greasy finish. They have low stickiness and moderate playtime.

Zettel detailed the results of a study on performance, tribology behavior and sensory analysis using an acrylate-based rheology modifier vs a combination of sclerotium gum, xanthan gum and pullulan. The study resulted in several key takeaways:

• Synthetic and natural rheology modifiers have different mechanisms of gelling and chemical structure resulting in different rheological performance and tribology behavior.

• Depending on the desired texture and sensory, using tools such as rheology and tribology can help screen the proper rheology modifier to use.

• Study showed correlated results on spreadability and tackiness.

• Such testing can help avoid expensive costs of running sensory panels.

“Hybrid combination of natural with low amount of synthetic rheology modifiers could be a good compromise to keep the naturality of the formula optimum, while not compromising on the texture and performance,” concluded Zettel, noting that more tests need to be conducted on other rheological modifiers such as modified biopolymer.

Rheological Warnings and Benefits

The Symposium’s final presenter, Ari Mayisoglu, Elementis, called rheology an “early warning system. It detects structural breakdown early, before visible separation or setting.”

Rheology monitors internal stress, viscosity and yield stress. It flags poor formulations quickly, reducing wasted development time. It signals phase separation, syneresis, settling, gelling and instability at various temperatures, according to the speaker.

Rheology imparts benefits, too.

“Good rheology, and by extension, good stability, help products deliver active ingredients on to skin more evenly,” said Mayisoglu.

The speaker detailed several tests formulators should consider when measuring rheology. The Amplitude Sweep reveals how much force a formulation can take before it breaks. It is critical for structural integrity and helps tune formulation brittleness vs flexibility. Viscosity Curve/Structural Recovery reveals shear-thinning behavior, assesses rebuild capacity after shear and indicates thixotropy or recovery lag. It predicts performance under mixing, pumping or application and informs whether the formulation can recover structure after shear.

Frequency Sweep tests reveal how the formula behaves over time under small, non-destructive forces. It evaluates network strength and elastic, and differentiates solid-like vs liquid-like behavior. Frequency Sweep determines long-term stability and resistance to settling or phase separation. Finally, Temperature Sweep assesses thermal stability of microstructures. It detects transitions or breakdown under heat.

“Temperature Sweep ensures formulations remain stable across temperature fluctuations during storage, transport or use,” explained Mayisoglu.

The Rheology Symposium is part of the NYSCC in-person events series. The New York, Long Island and New England chapters are organizing a ski trip January 30-February 1, 2026 at Killington, VT. NYSCC Suppliers’ Day is May 19 and 20, 2026 at Javits Center, New York.

Tom Branna is the former editor of Happi. He’s covered the global beauty, personal care and home care industry for more than 30 years. In his new role, he is consulting for suppliers and formulators in the industry. His email is tbranna@verizon.net.