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Shear stress is the force per unit area applied and 
shear rate is the resulting velocity gradient. 
Cosmetics experience shear rates varying 
from 0.001 s-1, from gravitational forces; 
to over 20,000 s-1, when a cream is spread or 
an aerosol antiperspirant sprayed (Fig 1). 
Cosmetics and Rheology
Strong partners to create the best possible products
The way the viscosity changes at varying shear rates 
greatly influences the overall product stability and 
performance. A material which maintains a constant 
viscosity, regardless of shear rate, has Newtonian flow 
(Fig.2). Dilatant flow (Fig.2) is a form where viscosity 
increases with shear, sometimes encountered in highly 
pigmented/filled systems. 
Pseudoplastic flow (Fig. 4), also known as shear thinning 
behaviour, and typical of many commercial systems, 
is when viscosity decreases with increasing shear rate. 
Flow may require a specific stress to be initiated. This 
particular stress value is known as the yield point.
A system having both shear thinning flow and a yield
point can be described as having plastic flow.
The rate of recovery of a system when stress is 
removed is also very important. When a shear 
thinning system shows delayed viscosity 
recovery, it is described as thixotropic (Fig.3). 
This is one of the most important types of flow in 
cosmetics. Controlling the degree of thixotropy 
enhances the application of a cream, eliminates 
dripping of a roll-on antiperspirant or allows 
brushmarks in a coat of nail lacquer to disappear, 
leaving a smooth film. 
Viscosity can be temperature dependent. 
Correct choice of rheological additive allows you to 
create the ideal flow characteristics (Fig. 1) and 
also achieve thermostable rheology. 
ELEMENTIS Specialties rheological additives can be 
broadly divided between aqueous-phase thickeners 
and non-aqueous-phase thickeners. 
But it is important to remember the advantages 
of oil-phase viscosity modification that can greatly 
improve emulsion based products. 
ELEMENTIS Specialties additives for cosmetics are 
based on naturally occurring materials: 
highly refined and beneficiated 
hectorite clay or castor oil derivatives. 
ELEMENTIS Specialties 
Rheological Additives 
for Cosmetics 
Improving aqueous, organic and 
emulsion-based products
 Hectorite - The benefits 
Hectorite is a unique swelling clay offering several 
advantages. Hectorite\u2019s special properties, compared 
with bentonite, are: 
\u2022 lower iron content \u2022 lighter colour \u2022	higher swelling capacity \u2022	greater gel strength \u2022	no crystalline silica
Due to its small size, platelet shape and large surface 
area, hectorite is able to form strong, stable viscous gels. 
Hectorite is a very effective thickener of water. Because 
of this and its other exceptional properties, it forms the 
basis of the BENTONE® hydrophilic clays. 
 BENTONE® Hydrophilic Clays
BENTONE® MA, EW, and LT rheological additives 
provide thixotropy and suspension control to the 
aqueous phase. 
BENTONE® MA and EW additives form gels by producing 
an open, 3-dimensional network of the individual clay 
platelets as shown in Figure 5. 
The two products are stable across the range pH 6-11 
and offer good tolerance to electrolytes. 
BENTONE® LT forms a similar network, 
but it is strengthened by the presence of a special 
cellulose, greatly enhancing stability and thickening 
characteristics. BENTONE® LT is stable across a 
broader range, pH 3-11, and is also the least 
electrolyte-sensitive product. 
BENTONE® MA and EW are in compliance with ECOCERT; 
The ecological and organic cosmetics standards.
Aqueous-Phase Additives
p u r e i n co s m e t i c s
INCORPORATION Hydrophilic Clays 
Wetting \u2022 Medium to high-shear mixing \u2022 Add clay to water before addition of other 
 ingredients \u2022 Disperse at moderate pH 
Shear \u2022 Low shear (< 10 ms-1) 
 = long mixing time (> 30 mins) \u2022 High shear (> 15 ms-1) 
 = shorter mixing time (10-15 mins) 
Time \u2022 10 minutes hydration before adding other 
Water at up to 60°C (140°F) reduces hydration time 
It is important to have only unadulterated water 
present at the dispersion stage. Surfactants or 
electrolytes should not be added until dispersion is 
For additional guidance see page 14
BENTONE® rheological additives are non-abrasive. 
The skin feel imparted by BENTONE® hydrophilic clays 
is a pleasant silkiness, quite different to that 
associated with the majority of cellulose, polymer 
and polysaccharide-based thickeners. 
Furthermore, as hectorite itself is insensitive to 
temperature variations, the BENTONE® products impart 
a thermostable viscosity control. 
Surfactants can influence the rheological behaviour 
of hydrophilic clays. 
Non-ionic surfactants, if they are highly ethoxylated, 
can adsorb onto the clay surface. This rarely causes 
problems either in flow control or activity of the 
Anionic surfactants can act as dispersing agents and 
weaken the gel structure. Alternatives that eliminate 
or minimise any problems can normally be found. 
However, cationic surfactants interact strongly and 
should be avoided. 
Organic and silicone-based liquids used in oil and 
wax-based cosmetics, and as the non-aqueous-phase in 
emulsions, benefit greatly from ELEMENTIS Specialties 
rheological additives. Outstanding rheological 
properties are developed using BENTONE® organoclay 
rheological additives in their powder form or, 
even better, with BENTONE GEL® additives, their 
predispersed forms. 
The benefits gained are: 
\u2022 thermostable viscosity control \u2022 thixotropic flow \u2022 suspension control of pigments and actives \u2022 emulsion stabilisation \u2022 silky skin feel 
 BENTONE® Organophilic Clays 
Hectorite is now reacted with special vegetable 
quaternary ammonium salts to produce organoclays 
able to thicken and gel organic liquids. The correct 
choice of BENTONE® additive is determined largely by 
the polarity of the system to be thickened. 
Additive Application
BENTONE® 27 V \u2022	Intermediate to high-polarity 
 organic systems such as esters 
 and triglycerides - for nail lacquers, 
 skin care, antiperspirants and 
 lip products
BENTONE® 38 V \u2022	Low to intermediate-polarity 
 organic systems such as volatile 
 silicones and mineral oil - for 
 antiperspirants, creams, lotions, 
 eye products and suntan products 
Non-Aqueous-Phase Additives
BENTONE® additives need to be efficiently dispersed 
using high-shear equipment and then to be activated 
with the optimum level of a chemical activator, such 
as propylene carbonate. 
BENTONE® organoclays form thixotropic gels by 
developing hydrogen bond bridges between the 
edges of adjacent platelets as shown in Figure 7. 
BENTONE GEL® additives are optimally dispersed 
and activated predispersions of ELEMENTIS Specialties 
Benefits include: 
\u2022 optimally dispersed 
\u2022 high-shear dispersion not necessary 
\u2022 no polar activation required 
\u2022 easy to handle and use 
\u2022 can be added at any appropriate and 
 convenient stage in manufacture 
A wide range of gels made from various cosmetics oils, 
esters and solvents are available. 
The use of a BENTONE GEL® enables you, the formula-
tor, to achieve the maximum efficiency from the 
 organoclay without the need for careful shearing and 
 activation. On the production scale, time is saved 
 and the highest degree of reproducibility attained, 
 leading to potenial cost savings. 
BENTONE GEL® additives can be added at any 
convenient suitable stage in the manufacturing cycle. 
BENTONE GEL® additives are very high-viscosity, shear 
thinning products. To ensure good homogeneous 
mixing is achieved, care must