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The wonderful world of hair
Anti-breakage
Anti-flyaway/static
Anti-frizz
Body
Color Protection
Conditioning
Control
Damage
Hold
Longevity
Manageability
Moisturization
Protection
Repair
Shine
Strength
UV Protection
Volume
Consumer attributes
Consumer language Scientific language
Anti-flyaway/static - electrostatic properties
Conditioning - lubrication
Moisturization - water content
Shine - light scattering
Softness - modulus
Strength - tensile properties
Volume - image analysis
Body - ???
There is danger in taking consumers’ words literally.
Consumer language -vs- scientific language
Technical assessment of hair performance
An experiment you’ve all probably tried
Conditioner
(master batch)
Conditioner
(sub-batch
#1)
Conditioner
(sub-batch
#3)
Conditioner
(sub-batch
#4)
Conditioner
(sub-batch
#2)
Consumer performance -vs- Technical performance
Technical performance win
Consumer performance gives loss/parity
Technical performance gives loss
Consumer performance gives loss
Technical performance equivalent
Consumer performance gives loss
Reformulate for improved
performance
Reformulate for improved
aesthetics?
Is the concept right?
Is the technical win off-set
by poor aesthetics?
Is the technical parameter
important?
The moisture content of hair
Dynamic Vapor Sorption (DVS)
Regulated Dry
Gas Flow
Microbalance
Mass Flow
Controller 1
Mass Flow
Controller 2
Temperature Controlled Incubator
Vapour
Humidifier
Sample
Holder
Reference
Holder
Temp/Humidity
Probes
Balance
Purge Adsorption isotherm for hair and water
Relative humditiy (%)
0 10 20 30 40 50 60 70 80 90 100
Am
ou
nt
ad
so
rbe
d (
%)
0
5
10
15
20 Evans - 2011
Speakman & Chamberlain - 1931
Weight increase and decrease as fn(humidity)
Time (mins)
0 1000 2000 3000
% In
cre
ase
in
we
igh
t
100
105
110
115
120
125
0 1000 2000 3000R
ela
tive
Hu
mid
ity (%
)0
20
40
60
80
100
DVS Data for virgin vs bleached/waved hair
Relative Humidity (%)
0 10 20 30 40 50 60 70 80 90 100
Incre
ase
in w
eig
ht (%
)
0
5
10
15
20
25
Virgin hair
bleached/waved
Cumulative increase in weight upon increasing humidity
Chemically damaged hair
will adsorb more water than
healthy hair
Technically, the term “dry
damaged hair” is an
oxymoron.
Hair contains highest
levels of moisture at high
humidity – a condition that
is synonymous with “bad
hair” days.
Inconsistencies between consumer
language and hair science
F.J.Wortmann, A.Hullmann, C.Popescu, Water
Management of Human Hair., IFSCC Magazine, Vol 10(4)
(2007) p317-320
“It is concluded that human hair exhibits a
rather robust static and dynamic water
sorption performance that, against initial
expectations, is not readily changed by
cosmetic processes and ingredients”.
P&G Study – Presented by MG Davis at 2009
DWI Hair Conference
• 20g ponytail hair tresses were treated with a non-conditioning shampoo
• Tresses were equilibrated for 48 hrs at either 15%RH or 80%RH
• Tresses were transported in plastic containers to maintain RH until evaluated by panelists
• Blindfolded panelists were asked to feel tresses and answer a series of questions (n=50)
Adsorption isotherm for hair and water
Relative humditiy (%)
0 10 20 30 40 50 60 70 80 90 100
Am
ou
nt
ad
sorb
ed
(%
)
0
5
10
15
20
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
More "Moisturized" Smoother More Tangled More Damaged
Attribute
% R
esp
on
se
15% RH
80%RH
No difference
Thanks to P&G for access and permission to present this data
P&G Study – Presented by MG Davis at 2009
DWI Hair Conference
Scanning electron microscopy
pictures of hair
Scanning electron microscopy
pictures of hair
Influence of hair type on combing results
Treatment
Maxim
um
com
bin
g forc
e (
gm
f)
0
10
20
30
40
50
60
Virgin hair Bleached hair Bleached & waved
hair
Effect of hair state on wet combing results
Untreated
Untreated
Untreated
XM XM XM
Typical wet combing results
Lubrication is behind claims
regarding –
Manageability
Conditioning
Protection
“Moisturization”
“Repair”
“Strengthening”
Lubrication and hair claims
Strong, Healthy Hair
Constant rate extension experiments
Schematic of stress-strain curve for wet hair
% Extension
0 10 20 30 40 50 60
Fo
rce
(g
mf)
0
20
40
60
80
100
Break Extension
Break Force*
Elastic (linear)region
Modulus = slope of linear region
*Note : Break Stress = Force/Cross sectional area
Plateau Load
Mean+SD
Mean-SD
Mean+SE
Mean-SE
Mean
Outliers
Extremes
Break Stress for chemically treated hairWet Tensile Testing (N=40)
Treatment
Bre
ak
Str
es
s
0. 011
0. 013
0. 015
0. 017
0. 019
0. 021
0. 023
V i rgi n B l eached B & WBleach &
waved
BleachedVirgin
Stress = force/unit area
Consumers do not assess the strength
of hair by stretching at a constant rate
and judging the force to break.
Consumer perception of “strength”
Brown & Swift (1975); Robbins (2006)
Hair fibers are plucked from the head
upon application of forces considerably
lower than the break force.
W.Hamburger, H.M.Morgan and M.M.Platt, Some aspects of
the mechanical behavior of hair, Proc.Sci.Sect., 14, 10-16
(1950)
Consumer perception of “strength” is likely related to number of fibers in
brush/comb after grooming; number of fibers in base of shower after
washing; and/or visual observation of split ends.
T.A.Evans, Fatigue Testing of Hair – A Statistical Approach to Hair Breakage, Journal of Cosmetic Science, 60, 599-616,
Nov/Dec, 2009
T.A.Evans and K.Park, A Statistical Approach to Hair Breakage. II. Repeated Grooming Experiments, Journal of Cosmetic
Science, 61, 439-455, Nov/Dec, 2010
T.A.Evans, Hair Breakage, in Practical Modern Hair Science, Ed. Trefor Evans & R.Randall Wickett, Allured Books, 2012.
T.A. Evans, Measuring Hair Strength, Part 2: Fiber Breakage, Cosmetics & Toiletries, Vol. 128(12), 854-859, December
2013
Single fiber fatigue experiments
The S-N Curve
“Break stress” by
conventional method would
be around 0.021 g/um2
So hair fibers will break (and break in a predictable manner) upon repeated application of stresses
considerably below the so-called “break stress.
Stress (g/um2)
0.009 0.010 0.011 0.012 0.013 0.014 0.015 0.016
Cyc
les to
fa
ilure
1e+1
1e+2
1e+3
1e+4
1e+5
1e+6
Failure cycles versus Stress virgin hairVirgin Caucasian hair at 60% RH
Repeated grooming experiments
Brushing Cycles
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
Num
be
r o
f b
roke
n fib
ers
0
10
20
30
40
50
60
70
80
90
100
Cumulative breakage as fn of grooming strokes
Unconditioned virgin and bleached Caucasian hair at 60% RH
Virgin hair
Bleached hair
Repeated grooming experiments
Brushing Cycles
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
Num
be
r o
f b
roke
n fib
ers
0
10
20
30
40
50
60
70
80
90
100
Cumulative breakage as fn of grooming strokes
Unconditioned and conditioned bleached Caucasian hair at 60% RH
Conditioned
Unconditioned Bleached hair
X times stronger claims
Fatigue leads to larger differences between samples
Stress (g/um2)
0.009 0.010 0.011 0.012 0.013 0.014 0.015 0.016
Cycle
s t
o f
ailu
re
1e+0
1e+1
1e+2
1e+3
1e+4
1e+5
1e+6
Failure cycles versus Stress virgin hair
Caucasian hair 60% RH
Hair type Average cycles-to-fail
Caucasian ≈ 37,000
Afro ≈ 5,500
Average number of cycles-to-fail for Caucasian and
Afro hair under repeated application of a 0.010
g/μm2 stress at 60% RH
Break stress for virgin Caucasian and Afro hair at 60% RH
Mean
Mean±SE
Mean±SD
Outliers
Extremes
Caucasian Afro
Hair type
0.012
0.014
0.016
0.018
0.020
0.022
0.024
0.026
Bre
ak s
tress (
g/u
m2)
≈ 9%
Fatigue leads to larger differences between samples
Stress (g/um2)
0.006 0.007 0.008 0.009 0.010 0.011 0.012 0.013 0.014 0.015 0.016 0.017
Cycle
s t
o f
ailu
re
1e+1
1e+2
1e+3
1e+4
1e+5
Failure cycles versus Stress virgin hair
Caucasian hair as fn(RH)
20% RH
60% RH
90% RH
Box Plot of Break Stress (gmf/sq. microns) grouped by % RH
Virgin Caucasian Hair at Different %RH
Mean
Mean±SE
Mean±SD
Outliers
Extremes20 60 90
% RH
0.012
0.014
0.016
0.018
0.020
0.022
0.024
0.026
0.028
Bre
ak S
tress (
gm
f/sq. m
icro
ns)
Relative Humidity Average cycles-to-fail
20% ≈ 24,800
60% ≈ 2,100
90% ≈ 100
≈ 4%
≈ 12%
Effect of RH on break stress
Average # cycles-to-fail for Caucasian hair under
repeated application of a 0.013 g/μm2 stress as fn RH
Stress (g/um2)
0.006 0.007 0.008 0.009 0.010 0.011 0.012 0.013 0.014 0.015 0.016
Cyc
les to
fa
ilure
1e+1
1e+2
1e+3
1e+4
1e+5
1e+6
S-N Curve virgin and treated Caucasian hair
60% RH
3x bleached
Hot-off-the-presses” data
Hot-off-the-presses” data
Stress (g/um2)
0.006 0.007 0.008 0.009 0.010 0.011 0.012 0.013 0.014 0.015 0.016
Cyc
les to
fa
ilure
1e+1
1e+2
1e+3
1e+4
1e+5
1e+6
S-N Curve virgin and treated Caucasian hair
60% RH
3x bleached
Virgin 90% RH
Hot-off-the-presses” data
Stress (g/um2)
0.006 0.007 0.008 0.009 0.010 0.011 0.012 0.013 0.014 0.015 0.016
Cyc
les to
fa
ilure
1e+1
1e+2
1e+3
1e+4
1e+5
1e+6
S-N Curve virgin and treated Caucasian hair
60% RH
3x bleached
Virgin 90% RH
3x bleached 90% RH
Hair type Average cycles-to-fail
Virgin (60% RH) ≈ 37,000
Bleached (60% RH) ≈ 2,700
Virgin (90% RH) ≈ 2,400
Bleached (90% RH) ≈ 150
Average number of cycles-to-fail under repeated
application of a 0.011 g/μm2 stress
% extension
Fo
rce (
gm
f)
90% RH
60% RH
Stress (g/um2)
0.006 0.007 0.008 0.009 0.010 0.011 0.012 0.013 0.014 0.015 0.016 0.017
Cycle
s t
o f
ailu
re
1e+1
1e+2
1e+3
1e+4
1e+5
Failure cycles versus Stress virgin hair
Caucasian hair as fn(RH)
20% RH
60% RH
90% RH
Fatigue testing as fn of RH
Schematic of Young’s modulus as fn RH
Glycerol treatment
Number of broken fibers as a fn of treatment after 10,000 grooming strokes
Mean
Mean±SE
Mean±SD
Outliers
Extremes
Control 10% glycerol
Treatment
0
10
20
30
40
50
60
70
# b
roke
n f
ibe
rs
Repeated grooming data
Relative Humidity Average cycles-to-fail
Virgin ≈ 33,200
10% glycerol ≈ 7,600
20% glycerol ≈ 2,600
Average # cycles-to-fail for Caucasian hair under
repeated application of a 0.011 g/μm2 stress at 60% RH
Stress (g/um2)
0.006 0.007 0.008 0.009 0.010 0.011 0.012 0.013 0.014 0.015 0.016
Cyc
les to
fa
ilure
1e+2
1e+3
1e+4
1e+5
S-N Curve virgin and treated Caucasian hair at 60% RH
60% Virgin
+ 10% glycerol
+ 20% glycerol
Adsorption isotherm for virgin Caucasian hair
Relative humidity (%)
0 20 40 60 80 100
Am
ou
nt
ad
so
rbe
d (
%)
0
5
10
15
20
5% citric acid
Changing the water content of hair – carboxylic acids
C.H. Nicholls, and J.B. Speakman, The adsorption of water by wool. Part IV – The influence of combined acid
on the affinity of wool for water., J.Tex.Inst., 45, T267-271, 1954
Binding of phenols by hair, Parts I, II and III, M.M.Breuer, J.Phys.Chem, 68, p-2067-2084, (1964). – showed
that water content is diminished by soaking hair in various phenolic solutions, with resorcinol showing the
largest effect.
Adsorption Isotherm for Water and Hair
Relative Humidity (%)
0 10 20 30 40 50 60 70 80 90 100
Am
ou
nt
ad
so
rbe
d (
%)
0
5
10
15
20
25
Virgin Hair
+ 5% resorcinol
Virgin Hair
Changing the water content of hair – phenols
Reduction in water content of hair after treatment with phenols
Relative Humidity (%)
0 10 20 30 40 50 60 70 80 90 100
Am
ount a
dso
rbe
d (
%)
0
5
10
15
20
25
+ 5% Cl-resorcinol
Virgin Hair
Changing the water content of hair – phenols
Fatigue testing on resorcinol-treated hair
Stress (g/um2)
0.009 0.010 0.011 0.012 0.013 0.014 0.015 0.016
Cycle
s t
o f
ailu
re
1e+1
1e+2
1e+3
1e+4
1e+5
Failure cycles versus Stress virgin hair
Caucasian hair
Virgin hair
Resorcinol soaked hair
The effects of acids on hair
Some companies are including carboxylic acids as
“actives”
Kao’s “3 Days Straight” product uses lactic and
malic acids as the active.
Glyoxylic acid is being pushed as an alternative to
formaldehyde-based BKT-type products.
Olaplex uses maleic acid as an active
Resorcinol activity as a function of soak time
Reduction in water content for hair after soaking in 5% resorcinol
Time (minutes)
0 20 40 60 80 100 120
% R
ed
uctio
n in w
ate
r co
nte
nt
0
5
10
15
20
25
30
35
Citric acid activity as a function of
temperature and soak time
Reduction in water content for virgin Caucasian hair after soaking in a 5% citric acid solution as a function of time and temperature
Time (minutes)
0 50 100 150 200 250
% R
ed
uctio
n in
wa
ter
co
nte
nt
0
5
10
15
20
25
22oC
40oC
Dynamic vapor sorption in Organics mode -
adsorption rate for hair and ethanol
Adsorption of water, ethanol and propanol by hair
Time (minutes)
0 200 400 600 800 1000 1200 1400 1600
Am
ount a
dso
rbe
d (
%)
0
1
2
3
4
0-10% jump in relative vapor pressure
Methanol
Ethanol
Water
Propanol adsorption
Adsorption of methanol, ethanol and propanol by hair
Time (minutes)
0 1000 2000 3000 4000 5000
Am
ou
nt
ad
sorb
ed (
%)
0
5
10
15
20
0-90% jump in relative vapor pressure
Methanol
Ethanol
Propanol
Adsorption testing with decane
Adsorption of decane by hair after 0-90% jump in relative vapor pressure
Time (minutes)
0 500 1000 1500 2000 2500 3000
Am
ou
nt a
dso
rbe
d (
%)
0.0
0.1
0.2
0.3
0.4
0.5
Rapid surface adsorption
Slow bulk adsorption
Adsorption and desorption of cyclomethicone on virgin hair after 0-90-0% steps in relative vapor pressure
Time (minutes)
0 500 1000 1500 2000 2500 3000
Am
ou
nt
adsorb
ed (
%)
0.0
0.1
0.2
0.3
Cyclomethicone
Adsorption testing with cyclomethicone
Adsorption of amyl acetate by hair after 0-90% jump in relative vapor pressure
Time (minutes)
0 1000 2000 3000 4000 5000 6000
Am
ou
nt
ad
sorb
ed (
%)
0.0
0.2
0.4
0.6
0.8
1.0
amyl acetate
Adsorption testing with amyl acetate
The rigors of hair
Hair Repair
The scope of the problem – what happens during
bleaching with a simple hydrogen peroxide solution?
Penetration of the solution between cuticle scales will weaken the inter-cuticular cement and leave
this protective structure more susceptible to deterioration.
Oxidative conditions, in combination with elevated pH, will irreversibly increase the swelling
capacity of fibers – placing additional strain on the cuticle structure each time the hair is wetted.
Degradation and dissolving of melanin pigment granules leads to lightening of the hair color while
seemingly leaving behind microscopic voids.
Oxidative side reactions with hair protein deplete strength-supporting cystine disulfide bonds by
conversion to cysteic acid.
Individual hair fibers become weaker and more prone to breakage.
The dry state modulus increases – leaving individual fibers stiffer
The lipid layer on the very outside surface of a hair fiber (the f-layer) is removed – changing its
interaction with water and possibly leading to slower hair drying.
Enhanced swelling in combination with a more-hydrophilic character can lead to increased fiber
water content.
Lipid structure becomes weakened and components are more easily removed.
What happens to hair during simple washing with a
standard shampoo?
Fibers swell - putting strain on the cuticle.
Swollen fibers are subjected to inter-fiber abrasion and friction - likely
causing cuticle wear.
Bending and twisting of fibers could initiate localized cuticle uplift.
Fibers encounter various tugging and fatiguing forces while in a
decidedly weaker, plasticized state.
Lipids and degraded protein may be leached from the hair.
Hair Damage - where does it occur?
Surface (cuticle)
Inside (cortex)
(Tactile, manageability, shine)
(Strength, breakage, stiffness) Mean+SD
Mean-SD
Mean+SE
Mean-SE
Mean
Outliers
Extremes
Break Stress for chemically treated hairWet Tensile Testing (N=40)
Treatment
Bre
ak
Str
es
s
0. 011
0. 013
0. 015
0. 017
0. 019
0. 021
0. 023
V i rgi n B l eached B & W
Bleach &
wavedBleachedVirgin
Hair Damage - how does it occur?
Chemical impetus
Mechanical impetus
Thermal impetus
Photochemical impetus
Hair Damage - how does it manifest to
the consumer
Manageability issues
Sensorial issues
Strength/breakage issues
Let’s combine the lot
Grooming-related surface damageSensorial-compromised hair due to grooming-
related surface damage
Repair Reduce Remove
Let’s combine the lot
Strength-compromised hair due to chemical-
related internal protein damage
Repair Reduce Remove
Summary
• Hair care products are sold using “consumer language”. This is the
language of our industry.
TRI-Princeton
• But……, • We should not forget we are scientists. Scientists are very precise people
who question everything.
• This can severely muddle our industry and the product development
process and often sends formulators off on wrong routes.
• Upon doing this, it becomes apparent that “consumer language” and
“scientific language” do not equate.
Shockingly blatant advertising
TRI-Princeton
Thank you for your attention
TRI-Princeton
