This document discusses camouflage colors and materials used in military applications. It provides details on: - The use of camouflage to conceal military equipment visually from enemies. - Sensor systems like active radars and passive cameras/night vision used as threats. - Principles of camouflage materials to mimic backgrounds like shape, shine and color. Green, brown, black, and olive hues are commonly used. - Types of camouflage for different spectra like UV, infrared, and multi-spectral designs. Specific dyes and pigments used for fabric dyeing and coating materials are outlined. - An experiment dyeing cotton fabric with vat dyes to

1. CAMOUFLAGE COLOURS IN MILITARY
APPLICATIONS
INDIAN INSTITUTE OF TECHNOLOGY, DELHI
PRESENTED TO PROF. M. L. GULRAJANI
Arka Das
2012TTF2404

2. Military Camouflage
 Military camouflage is the use of camouflage by a military force to protect
personnel and equipment from visual observation by enemy forces.
 In practice, this means applying colour and materials to military equipment
of all kinds, including vehicles, ships, aircraft, gun positions and
battledress, either to conceal it from visual observation (crypsis), or to
make it appear as something else (mimicry).

3. Sensor Systems in Military Applications
 Active. Active sensors emit energy that reflects
from targets and is recaptured by the emitting
or other nearby unit, indicating the presence
of a target. Examples of active sensors are
searchlights and radars.
 Passive. Passive sensors emit no energy. This
type of sensor collects energy, which may
indicate the presence of a target. Examples of
passive sensors are the human eye, night
vision devices, and photographs.

4. Threats in Military Applications
 Image Intensifiers
 Low-Light Television (LLTV).
 Aerial Reconnaissance, Remote Sensing, and
Imagery
 Near Infrared (NIR) Sensors
 IR Sensors
 UV Sensors
 Radar

5. Camouflage Systems
 The aim is to make sure that the surface of the soldiers and not
form a contrasting shape against the background.
 The principles involved in camouflage materials are
shape, shine, shadow, silhouette, surface, spacing and
movement .
 The hues used in the camouflage are
green, olive, khaki, brown and black.

6. Factors influencing Camouflage
 Contrast of brightness
 Contrasts of colour
 Contrasts of texture
 The geometry of boundaries between contrasting
zones
 Distribution of contrasts in the visual field
 Previous experience of the subject

7. Types of Camouflage
 UV camouflage
 Camouflages for visible region
 NIR camouflage
 Thermal IR camouflage
 Anti radar camouflage
 Camouflages for multiple spectra

8. UV camouflage
 Only in the snow covered environment is UV observation of
military importance.
 Titanium dioxide pigment which is commonly used as a low-
cost widely available treatment for artificial fibres is visually
white, but has low reflectance in the UV.
 Luckily, other pigments such as barium sulphate are
suitable and can be incorporated into textile coatings.

9. UV camouflage

10. Camouflages for visible region
 In this range we are trying to mimic natural or even
artificial backgrounds, not just in terms of colour,
but also patterns, gloss and texture.
 A tree or bush, for instance, will have a different
appearance during different parts of the day as the
quality of illumination changes.
 In practice, each military nation has adopted its own
visual colours and patterns. Colours often include
khaki, green, brown and black, with additional
colours such as olive, yellow, orange, pink, grey,
beige, and sand to extend use to other urban, rural
and desert backgrounds.

11. Infra red rays
 Infrared (IR) light is electromagnetic radiation with a
wavelength longer than that of visible light.
 It is measured from the nominal edge of visible red light
at 0.74 micrometres (µm), and extending conventionally to
300 µm.
 These wavelengths correspond to a frequency range of
approximately 1 to 400 THz, and include most of the thermal
radiation emitted by objects near room temperature.
 Microscopically, IR light is typically emitted or absorbed
by molecules when they change their rotational vibrational
movements .

12. Types of Infra red rays
The CIE recommended the division of IR into following three
bands.
Near Infra red – 700 – 1500 nm
Middle Infra red – 1400 – 3000 nm
Far Infra red – Above 3000 nm.

13. Near Infrared Camouflage
 The development of infrared surveillance technology
during the Second World War has had a particularly
significant effect on the challenge of supplying
military personnel and equipment with effective
means of concealment.
 It has forced the evolution of a generation of
camouflage materials that attempt to minimise the
contrast between objects and their environment over
the near infrared region of the electromagnetic
spectrum in addition to the visible region.

14. IR reflectance of natural surroundings
 NIR range – 700 – 1200 nm.
 The sand and soil show a slight
rise from visible region to those
in the infrared.
 As moisture content increase
reflectance in visible region
decrease in the soil.
 Plants tend to have a small
increase in reflectance at around
550 nm, which is responsible for
the green coloration. Reflectance
then decreases slightly in the red
region and rises steeply between
680 and 710 run to a plateau at
720 nm. At longer wavelengths
the reflectance remains fairly
constant until about 1300
nm, where it decreases again.

15. Contd..
 Black camouflage tends to have low,
near-constant reflectance values.
 Brown hues have gradually rising IR
curves typical of sand and soil.
 Green shades must duplicate the
'chlorophyll increase' or 'edge' .
 Generally, military authorities require
green camouflage to exhibit a steep rise
in reflectance between 700 and 720 nm,
so that reflectance in the range 700-900
nm exceeds that in the 600-690 nm
region .

16. Dyeing of cellulosic fibres
 Vat dyes absorb IR are suitable for military
uniforms as well as the required fastness to
light and washing.
 Certain sulphur dyes exhibit low IR reflectance
but not used in camouflage due to poor light and
wet fastness.
 In Table 1, Combination of Cibanone (Ciba) or
Indanthren (BASF) ranges of vat dyes are shown.
 Suitable vat dyes are generally based on
anthraquinonebenzanthrone- acridine polycyclic
ring systems.

17. Vat dye combinations for camouflage for
cellulosic
Shade Dyes
Pale CI Vat Brown 6 ((Cibanone Brown F3B)
Brown CI Val Brown 1 (Cibanone Brown FBR)
CI Val Orange 15 (Cibanone Golden Orange F3G)
Dark CI Vat Brown 35 (Cibanone Yellow Brown FG)
Brown CI Vat Black 27 (Cibanone Olive F2R)
CI Vat Red 24 (Cibanone Red F4B)
Pale CI Vat Green 28 (Cibanone Green F6G)
green CI Vat Black 27 (Cibanone Olive F2R)
CI Vat Orange 15 (Cibanone Golden Orange F3G)
Dark CI Vat Green 28 (Cibanone Green F6G)
green
CI Vat Black 27 (Cibanone Olive F2R)
Cibanone Brilliant Green F4G
Grey CI Vat Black 30 (Cibanone Grey FOGR)
CI Vat Brown 35 or CI Vat Orange 15
CI Vat Black 27 (Cibanone Olive F2R)

18. Olive green shades  Suitable vat dyes are generally
based on
anthraquinonebenzanthrone-
acridine polycyclic ring systems
 CI Vat Green 3 (X = Y =
H), prepared by condensing 3-
bromobenzanthrone with I-
aminoanthraquinone and fusing
the product with alkali
 Examples of these olive dyes
include: (X = H, Y = NHCOAr), (X
= Ph, X = H, Y = (4-
halogeno)anthraquinyl-1-amino)
and (X=H, Y= SC4H9)
CI Vat Green 3

19. Grey & Olive shades
 2-methyl-1(3)- anthraquinylamino
substituent in one of the α-positions of the
anthraquinone residue.
 Synthesised by condensation of 3-
bromobenzanthrone &
diaminoanthraquinone, reacted with a
bromoanthraquinone.
 The subsequent alkali treatment is claimed
to cause a double ring closure, i.e. the
formation of two acridine residues.

20. Olive brown shades
 Anthraquinone-benzanthrone- acridine
dyes are those of general structure (5; R
= H, X = NHCOAr).
 For example, analogues of CI Vat Black
25 (5; R = X = H). The derivatives (5; R
= (cyclo)alkyl, X = H)
 Infrared reflectance of about 10-25%.
 The dyes (5; R = H, X = OCH3) and (5;
R = H, X = SC4H9) are claimed to give
CI Vat Black 25
grey and brown shades, respectively on
cotton

21. Olive & Brown shades
 Anthraquinone-benzanthrone-acridine
derivatives, containing a thiaxanthone
residue, prepared 4-aminoanthraquinone
thiaxanthone.
 The dyes yield olive to brown shades on
cotton of low infrared reflectance
 They give satisfactory light and wash
fastness properties.

22. Dyes for Non cellulosic fibres for camouflage
 Strongly IR absorbing pigments, such as
carbon black, can be melt-spun into or
printed onto the polymer to raise IR
absorption.
 PET fabric dyed with the disperse dyes (8; X
= NHCH,OH, Y = OH; 0.2% o.m.f.), (8; X
= OH, Y = NHCH,OH; 0.2% 0.m.f.) and 9
(0.8% o.m.f.), by a carrier dyeing method.
 These doesn’t have satisfactory IR.
 So, PET spun-dyed with carbon black (0.01
% by weight) and cross-dyed with the
same dye combination is claimed to have
superior reflectance characteristics which
meets the criteria of the Danish Army.

23. Dyes for other fibres
 Camouflage shades can be produced in this fashion from polyamide fibres
(disperse, non-metallised acid or metal-complex dyes), cellulose acetate
(disperse dyes) and viscose (reactive dyes).
 In the case of wool, only a few green and black colorants absorb
sufficient IR to be suitable for camouflage purposes.
 Using other dyes the required IR can be obtained by forming a blend
with suitably dyed or spun viscose or synthetic fibres
 If 100% wool materials are required, IR can be lowered by fixing carbon
black onto the fibre with a synthetic resin binder.

24. Pigments used for IR camouflage
Organic Pigments Inorganic pigments
Perylene black Chromium oxide
Phthalocyanine blues Red & yellow oxide of iron
Greens Ferric oxide
Violet Carbon black
Carbazole dioxazine Lead chromate
Carbon black
Metallic pigments
Quinacridone
Isoindolinone
Isoindoline
Diketopyrrolopyrrole
The particle size of the pigment should be 0.35 – 0.55 microns
For highest reflectivity, the particle size should be more than half
the wave length of the light to be reflected.

25. Camouflage of Cotton Fabrics in Visible
and NIR Region Using Three Selected
Vat Dyes
To provide camouflage in near infrared (NIR)
region and imitate reflectance profile of greenish
leaves, cotton fabrics were dyed with three
selected vat dyes, namely C.I. Vat Blue 6, C.I. Vat
Yellow 2, and C.I. Vat Red 13.
Reflectance curves of two types of fresh greenish
leaves were measured as standard reference.

26. Experimental Details
 Cotton fabrics with twill weave (bleached and
mercerized) were purchased from Ardakan textile (Yazd,
Iran).
 C.I. Vat Blue 6, C.I. Vat Yellow 2 and C.I. Vat Red 13
were used.
 For dyeing process, 1 g of dye powder was added to 99
mL distilled water at 60–70°C and stirred for 10 min.
 1% owf (on weight of fiber) solution of each dye was
prepared.
 For reduction of vat dyes, th required amount of dye was
added to dye bath, then 36 mL/L alkali and 36 g/L
sodium hydrosulfite for NATO green shade and 51.5
mL/L alkali and 51.5 g/L sodium hydrosulfite for forest
green shade were added to dye bath.
 Temperature of dye bath was adjusted to 40°C.
 After this time, temperature raised to 60°C, and the
dyeing process was continued for 40 min.

27. Dye Structure
As above
mentioned, vat dyes
which have
anthraquinone, benzant
hrone, or acridine
polycyclic ring
structures are suitable
for camouflage in NIR
region and create
suitable spectral
reflectance.5 So in term
of structure, they are
appropriate for
camouflage in NIR
range.

28. RESULTS AND DISCUSSION
 In reflectance profile of
green leaf there is a
slight increase in range
of 550 nm.
 Then in range of about
670–780 nm, the
reflection increases
steeply.
 These amounts for
deciduous leaf and
coniferous needle are 90
and 50%,

29.  From Fig. 5, it can be
concluded that for Vat
Yellow 2 there is an
absorption peak around
422 nm in visible range.
 There is an absorption
peak around 520 nm for
Vat Red 13.
 The absorption peak of
Vat Blue 6 occurs at 660
nm.

30.  It can be observed that the
reflectance of Vat Yellow 2
increases sharply within the
range of 440– 560 nm. After
this range, reflectance will be
constant in about 67±2%
 The reflectance of Vat Red 13
increases rapidly in range of
580–700nm. Then reflectance
is 64±6% until 1100 nm. Also
for this dye, there is an
increase around 420 nm.
 The reflectance of Vat Blue 6
increases in range of 700–780
nm and also for this dye there
is a pronounced increase
around 440 nm. After 780 nm,
the reflectance will be in range
of 59±2%.

33.  From Figure 9, it can be
seen that general shape
of the reflectance curves
is very similar to
reflectance profile of
greenish leaves.
 Both of them have slight
increasing in about 550
nm and also have
pronounced increasing in
range of 670–780 nm
according to reflectance
profile of green leaves.

36. Summary
 Three vat dyes were selected (Vat Blue 6, Vat yellow 2,
and Vat Red 13) and cotton fabrics were dyed with these
dyes to imparting camouflage in NIR region and similarly
with the reflectance profile of green leaves.
 Compared with the reflection curves of C.I. Vat Yellow 2
and C.I. Vat Red 13 and green leaf, the reflectance profile
of Vat Blue 6 is very similar to reflectance curve of
greenish leaves in range of 670–780 nm.
 For Vat Blue 6, the reflectance curve of dyed fabrics
matches with reflectance of leaves at dyeing
concentration of 0.85% owf and 1.2% owf, for NATO and
forest green shade, respectively.
 The dyes have suprerior wash and light fastness and
their camouflage characteristics do not change during
exposure.

37. Thermal infrared camouflage waveband
 The thermal or far infrared (FIR) wavebands are,
militarily, defined as being from 3–5μm, and 8–14μm.
 Objects are detected by the heat energy they emit or
reflect.
 The relationships between energy emitted, emissivities,
wavelengths, and temperatures are covered by
mathematical relationships derived by Planck,Wien, and
Stefan. In simplified terms these are:
 λmax*T = a (constant)
Where λ is the wavelength and T is absolute temperature
Stefan; E = ησT^4
η is the emissivity and σ is a constant

38. Thermal infrared camouflage waveband
Therefore, there are two things that we can do to reduce
the thermal signature of targets, reduce the temperature
and the emissivity of the target.
1) Reduce the temperature of the target: vehicles need to
be designed so that hot exhaust systems are cooled by
air or liquids, by insulating the hot components, or by
rerouting the hot piping so that it is covered and not
visible.
2) Reduce the emissivity of the target: Most surfaces are
good emitters, except those which are shiny and
metallic. Therefore, we can lower the emissivity of the
target by using a shiny reflective cover, although this
will obviously interfere with visual camouflage

39. Radar
MTI Radar.
(a) MTI radar is a threat to ground forces near the
battle area. Radar-reflecting metal on dismounted
soldiers has been reduced. Kevlar helmets and body
armor are now radar-transparent. Plastic canteens
are standard issue. Velcro and buttons have
replaced metal snaps on most field uniforms. A
soldier wearing only the BDU cannot be detected
until very close to an MTI radar.
(b) Vehicles are large radar-reflecting objects. Moving by
covered routes protects against MTI radar
surveillance

40. Conclusion
 The development of several surveillance technology has
rendered obsolete textile production techniques that
provide camouflage solely in the visible region of the
electromagnetic spectrum.
 Modern military forces require counter surveillance
materials that afford protection against several
surveillance technology, camouflage textiles must satisfy
for all threats.
 The ease of fulfilling such requirements varies with the
substrate of the camouflage material. Conventional
methods for the coloration of other fibers have been
found to be inadequate. Novel dyes and pigments, as
well as new techniques, have had to be developed in
future.

41. References
1) Infra red camouflage, S M Burkinshaw, G Hallas & A D
Towns, Rev. Prog. Coloration, 26 (1996) 47.
2) HANDBOOK OF TECHNICAL TEXTILES, A R Horrocks and S
C Anand, Woodhead Publishing Limited
3)Camouflage Textiles, D.Saravanan, AATCC Review, 2007.
4) Camouflage of Cotton Fabrics in Visible and NIR Region Using
Three Selected Vat Dyes, U. Goudarzi, J. Mokhtari,* M.
Nouri, Wiley Periodicals, Inc., 29 June 2012
5) Introduction to camouflage & deception, Dr.J.V.Ramana
Rao, DRDO, DESIDOC, 1999.
6) Infrared Reflective Inorganic Pigments, Ashwini KB & Vinod
CM, Recent Patents on Chemical Engineering, 2008, 1, 67-79
7) Wikipedia
8) Camouflage Colours, T. y. OVERTON, Stores and Clothing
Research and Development Establishment, Ministry of
Dejence, Flagstafl Road, Colchester, Essex

42. THANK YOU