Glossary of Banknotes

ANTI-SCAN / ANTI-COPY PATTERN

An image constructed of parallel and multidirectional fine lines or raster units. The pattern parameters (direction, width of strokes and the distance among them) impedes reproduction of the images by copying equipment which can be seen as moire or a darker (lighter) text compared with the background (fig. 1, fig. 2).

Fig. 1. Offset with rainbow printing.  10 Turkish Lira (2005)

Fig. 2. Offset.  5 Uzbekistan Sum (1994)

ANTI-STOKES INK

An ink, containing crystals of rare-earth metals, which glows when exposed to IR light of high intensity. When viewed in such spectrum, the surface of the image looks like a brightly glowing printed area or dots (fig. 1).

Fig. 1. Anti-Stokes fluorescence. 5 000 Russian Rubles (1997).  Images of anti-Stokes fluorescence of banknotes are available in the Forensic version of the Database

BACKGROUND PATTERN

A regular or irregular background drawing executed by thin continuous, often intertwining lines with observance of a number of rules (lines have no gaps, thickenings in points of intersection and so forth) (fig. 1). It is a variety of guilloches.

Fig. 1. Background pattern. 500 Ukrainian Hryven (2006)

BAR-CODE

A sequence of parallel lines (bars) which vary in their widths and spaces between them and store data readable by special devices. A bar-code is usually printed by letterpress; its ink may contain additional security properties (e. g. magnetic pigments) (fig. 1).

Fig. 1. Bar-Code. 100 000 Lebanese Pounds (2004)

BLIND EMBOSSING

A colourless relief image applied on a coloured or unstamped area of the banknote by pressure or heating which deform the substrate. It is a palpable image used both in paper and polymer banknotes (fig. 1); is visible under oblique light. A coloured image gradually transforming into blind embossing is a more intricate security feature (fig. 2).

Fig. 1. Blind embossing on the clear window. 20 Mexican Pesos F series (2006). Polymer substrate

Fig. 2. Coloured image gradually transforming into blind embossing. 1 000 Yemeni Rials (2009). Paper substrate

CLEAR WINDOW

A transparent area of the polymer banknote created during the manufacturing process of the substrate, not covered with any coatings.

Classification

Depending on the design and security features:

• simple clear window (fig. 1, a);
• with vignette (image, text, etc.) (fig. 1, b);
• with embossing;
• with metallized covering (coating);
• with colour changing effect;
• combined (several effects).

a	b
Fig. 1. Clear window: a – simple. 2 000 Chilean Pesos (2004); b – with vignette. 20 Brunei Dollars (2007)

DIFFRACTIVE IDENTIFICATION FEATURE DID

DID – Diffractive Identification Device

An optically variable feature formed by a coating with the effect of polarization. A colour shift is observed, while rotating the image in its own plane by 90° (fig. 1).

a	b
Fig. 1. DID Patch. 500 Philippine Pesos (2010): a – without rotation; b – rotated by 90°

DIFFRACTIVE OPTICAL ELEMENT WinDOE

DOE – Diffractive Optical Element

An optically variable device that appears in a transparent window and is only visible in transmitted light with the assistance of a distant point light source. The transparent window is transformed into an image (usually a banknote denomination) via light diffraction. This device is unique for its ability to be seen best at night or against dim light (fig. 1).

a	b
Fig. 1. Diffractive optical element WinDOE. 50 Kina of Papua New Guinea (2010): a – view under reflected light ; b – view in transmitted light. WinDOE is placed in front of a distant point light source

DYNAMIC COLOUR SHIFT G-SWITCH

A security feature of the banknotes on the polymer substrate in the form of an image which changes its colour, when changing the angle of view. The effect is achieved due to the “multilayer” structure of the coating and may be seen, when changing the angle of view (fig. 11). It is similar to OVI for the banknotes on the paper basis.

a	b
Fig. 1. Dynamic Colour Shift G-Switch. 10 Hong Kong Dollars (2007): a – view at right angles; b – view of the tilted banknote

FOIL STAMPING

A relief and (or) a coloured image produced by stamping a metallized film or foil to the surface of the banknote. Due to high pressure, parts of the foil get into the paper making its mechanical separation practically impossible.

If diffraction foil is used, the image may change colour when the banknote is tilted (fig. 1).

a	b
Fig. 12. Foil stamping: a – 50 Brunei Dollars (1996); b – 20 Bahamian Dollars (2006)

GRAVURE PRINTING

A printing technique from a plate, where printing elements are incised into the surface and consist of very small cells separated by thin dividers (raster cells) regardless of the type of the image (a text or an illustration). These dividers and other spacing elements rise and lie on the same level. The printing plate is made on the cylinder. During the printing process, first of all a low-viscosity ink is applied in plenty over the whole surface of the rotating plate. Then a special knife (scraper), sliding along the plate surface, removes totally the ink from the spacing elements and its excess from the printing elements. The ink is transferred under contact pressure from the printing elements to the substrate.

The characteristic features of the prints:

• absence of outlined contours or lines (fig. 1);

Fig. 1. Fragment printed by gravure printing. 100 Mexican Pesos F series (2007)

• raster lines of spacing elements may be seen in the places of light halftones (fig. 2, a);
• absence of bulges or coloured relief;
• notched edges of the image (fig. 2, b).

a	b
Fig. 2. Zoomed fragment printed by gravure printing. 100 Mexican Pesos F series (2007): a – raster lines of spacing elements; b – notched edge of the image

Gravure printing is used in the manufacturing process of the banknotes on the polymer substrate.

GUILLOCHES

An intricate geometrical pattern formed by superposition of several relatively simple fine curved lines, constructed according to certain mathematical laws. A similar guilloche cannot be constructed without these mathematical laws. Guilloche designs form rosettes, frames, borders, vignettes and other images, as well as the elements of background patterns. A pattern can consist of either negative or positive lines (fig. 1).

Fig. 1. Negative and positive guilloches. 500 Burundi Francs (1988)

HALF WINDOW

A variety of a clear window, with one side of the banknote opacified. It is created during the manufacturing process of the polymer substrate. The resulting effect is a glossy surface on one side, while the other side becomes a normal printing surface (fig. 1).

a	b
Fig. 1. Half Window. 5 Malaysian Ringgit (2004): a – transparent side; b – opacified side

HIDDEN MULTI-COLOUR (HMC) IMAGE

An image made by colorless embossing over a printed area on the banknote. When the banknote is tilted, the image appears on the one-coloured area of the banknote. Each character of the image has its own colour. When the banknote is rotated without changing the angle of view, each character changes its colour (fig. 1).

When the banknote is tilted under UV light, the image may appear on the one-coloured area of the banknote. Each character of the value numeral has its own colour. When the banknote is rotated without changing the angle of view, each character changes its colour (fig. 2).

a	b
c
Fig. 1. Hidden Multi Coloured image under white light. 500 Russian Rubles (1997). Modification 2010: a – view at right angles; b – view of the tilted banknote; c – view of the tilted and rotated banknote
a	b
c
Fig. 2. Hidden Multi Coloured image under UV light. 500 Russian Rubles (1997). Modification 2010: a – view at right angles; b – view of the tilted banknote; c – view of the tilted and rotated banknote

HOLOGRAM / KINEGRAM

A diffractive optically variable device. The holographic image is formed by diffraction and refraction of light on gratings and changes at different angles of illumination and observation (fig. 1–6).

a	b
Fig. 1. Effect of image movement: the digital symbol of the nominal is moving in the horizontal direction. 50 Yuan Renminbi (1999): a – view at right angles; b – view of the tilted banknote

Security features:

• changing of the image colour at different angles of illumination and observation (fig. 2);

a	b
Fig. 2. Effect of colour changing. 1 000 Danish Kroner (2009): a – view at right angles; b – view of the tilted banknote

• changing of images at different angles of illumination and observation (kinetic effect) (fig. 3);

a	b
Fig. 3. Image changing (rotation). 200 Croatian Kuna (2002): a – view at right angles; b – view of the tilted banknote

• pseudovolume effects, images visually perceptible as located at different depth (fig. 4);

a	b
Fig. 4. Pseudovolume effect. The bird seems to move behind the portrait. 100 Gambian Dalasis (2010): a – view at right angles; b – view of the tilted banknote

• microtexts and nanotexts (fig. 5);
• latent images visualized by a laser beam using special devices;
• laser demetalization (fig. 6).

Fig. 5. Microtexts. 50 Danish Kroner (2009)

Fig. 6. Demetalization. 20 Euro (2002)

INTAGLIO

A printing technique from a plate, where printing elements are incised into the surface. Spacing elements are above the printing ones. A viscous ink fills in the recessed areas of the printing plate and is transferred to the substrate under high pressure (80–100 kg/cm2). The pressure forces the substrate into the recessed areas.

Characteristic features of the prints:

• a thick ink layer which produces relief;
• a wide range of tone transfers due to different depth and width of strokes;
• substrate deformation (inward bulging from reverse side);
• ink creeping between paper fibers at strokes edges (fig. 1).

Polymer banknotes may not have ink creeping.

a

b

Fig. 25. Zoomed area of the image printed by intaglio. 500 Hong Kong Dollars (1997): a – front side, showing a wide range of tone transfers and ink creeping at strokes edges; b – reverse side, showing paper deformation (inward bulging) at the printed area

INTAGLIO CONTRAST EFFECT (ICE)

ICE – Intaglio Contrast Effect

An image printed with special inks by intaglio over the metal coated area of the polymer banknote. The element has an optically variable colour effect: the colours of the image become more contrasting when looking at the banknote at a very sharp angle (fig. 1).

а	b
Fig. 1. Intaglio contrast effect (ICE). 100 Brunei Dollars (2004): a – view at right angles; b – view at a sharp angle

IR-FLUORESCENT INK

An ink, containing fluorescent substances (pigments) which glow white when exposed to visible infrared (green) light (wavelength is 400–530 nm). It may be coloured of coloureless. The pigments are not visible under normal daylight; can be detected by special devices (fig. 1).

Fig. 1. IR fluorescence of images, banknote denominations and security fibers.  5 000 Serbian Dinars (2010). Images of IR fluorescence of banknotes are available in the Forensic version of the Database

IR-METAMERIC INKS

Inks, which possess similar spectral properties under usual white illumination (look like of the same colour) and have differences in infrared spectrum (wavelength of 870 nm). Some inks are IR-absorbing and others are IR-reflecting. As a result, when examining the banknotes using special devices, only IR-visible images can be seen in the device monitor (fig. 1).

Infrared protection is based on the property of the material (pigments) to absorb or to reflect IR light.

a	b
Fig. 1. Location of IR-absorbing and IR-reflecting inks on the banknote. 200 Euro (2002): a – white illumination; b – view under infrared light

IRIDESCENT INK

A semi-transparent ink with a nacreous glitter (fig. 1, a). It contains transparent pigments consisting of tiny mica scales covered with a thin film (fig. 1, b). The pigments cause interference of incident light and produces the colour changing effect, when changing the angle of view or entrance. The iridescent element is not seen at right angles.

a	b
Fig. 1. Iridescent ink. 100 Netherlands Antillean Guilders (2006): a – applied as a composition. View under oblique light; b – zoomed area of the image

KALEIDOSCOPE

A complex security feature developed by De La Rue Company. It is an image printed on a foil substrate. The high relief image is applied by intaglio. The kaleidoscopic effect appears in the image when the banknote is rotated clockwise (anti-clockwise). This effect is characterized by illusory motion of alternating light and dark geometric figures from the center to the periphery. The distribution of light and dark areas in the image is determined by the shape of the strokes, ink relief and illumination.

a

b

c

d	e	f
10 Fiji Dollars (2012): a — front side of the banknote, Kaleidoscope element location; b, c, d, e — kaleidoscopic effect at different angles of illumination; f — fragment of a dodecagonal star printed by intaglio on a foil substrate

LATENT IMAGE

An image formed by the parallel lines printed at an angle to the lines of the background. Usually printed by offset. The printing technique and colours of the image and the background are integral and the image in indistinguishable by the naked eye (fig. 1).

Visible with magnifying devices as an alphabet character, a numeral or a geometrical figure (fig. 1).

а

b

Fig. 1. Latent image 20 Mozambique Meticais (2011). a – image of a banknote showing the location of the element (the latent image is indistinguishable); b – zoomed image of the latent image

See also latent image MASK, latent image PEAK, latent image KIPP, latent scrambled image.

LATENT IMAGE KIPP

An image formed by the lines printed by intaglio perpendicularly to the lines of the background. When the banknote is viewed at an acute angle, the image becomes visible on the background. It becomes either light on a dark background or dark on a light background. The lines parallel to the direction of eyes look light, and the perpendicular lines look dark. Therefore, the tone of the background and the image change, when the bill is rotated without changing the angle of view (fig. 1).

a	b	c
Fig. 1. Latent image KIPP. 1 000 Russian Rubles (1997). Modification 2010: a – view at right angles; b – view at an acute angle; c – view at an acute angle after banknote rotation

LATENT IMAGE MASK

An element consisting of two images made by different printing methods with the same colour. The first (bottom) image is printed by offset, the second image is printed by intaglio over the first one. The top image can be observed under reflected light, the lower image becomes visible in transmitted light (fig. 1).

a	b
Fig. 1. Latent image MASK. 20 Gibraltar Pounds (2011): a – view under reflected light; b – view in transmitted light

LATENT IMAGE PEAK

PEAK – Printed and Embossed Anticopy Key

An image made by colorless embossing over a printed area on the banknote. The result is an optically variable element which is palpable. The latent image becomes visible under oblique light (fig. 1).

a	b
Fig. 1. Latent image PEAK. 20 Liberian Dollars (2003): a – view at right angles; b – view under oblique light

LATENT IMAGE PEAK WITH IRIDESCENT COVERING

Integrated optically variable security element, which comprises:

1. latent image PEAK;
2. iridescent ink.

The latent image and iridescent covering become visible under oblique light (fig. 1).

a	b	c
Fig. 1. Latent image PEAK with iridescent covering 2 000 Mauritanian Ouguiya (2011): a – without tilting; b, c – tilted (different angles)

LATENT IMAGE WITH MULTI-COLOUR KIPP-EFFECT PEAK-PIXEL

A latent image made by blind embossing on a substrate printed with raster dots (pixels). It is viewed in oblique light at an acute angle. Embossed hemispherical elements are made in such a way that they have pixels of different colours on their opposite side surfaces. Depending on illumination direction, one of the two colours becomes bright and intense. This colour determines the overall hue of the image. As a result, the raster substrate and embossed structure interact with each other to produce the KIPP-effect with a colour shift.

a

b

c

d	e	f
Latent image with multi-colour KIPP-effect. 500 UAE Dirhams (2013): a — view at a right angle in incident light; b, c — view at an acute angle at opposite illumination directions; d — location of coloured raster dots on side surfaces of the embossed elements; e — oblique illumination at an acute angle on the right: the latent image becomes green, red dots are shaded; f — oblique illumination at an acute angle on the left: the latent image becomes red, green dots are shaded

LATENT SCRAMBLED IMAGE

An image formed by differences in the patterns of the element and the background. The encoding process can combine multiple images and make them look as one. The images become clear only when viewed through a specially manufactured decoder lens (fig. 1, b).

a	b
Fig. 1. Latent scrambled image. 100 000 Indonesian Rupiah (2004): a – without a special decoder ; b – with a special decoder

LETTERPRESS

A printing technique, in which the ink is printed on the substrate from a printing plate with printing elements raised above spacing elements.

Since printing is carried out under high pressure (15 kg/cm2), the prints have the following characteristic features:

• uneven ink distribution in the strokes: less in the middle than along the edges;
• a rim formed by the ink along the edges of a stroke (“beaded edges”) (fig. 1, a);
• substrate deformation (protuberance on the back side of the print (fig. 1, b); inward bulging on the front side of the print).

Letterpress printing is often used for printing serial numbers and bar-codes on the banknotes.

a	b
Fig. 1. Zoomed area of the image printed by letterpress. 100 Danish Kroner (2009): a – front side of the print; b – showing paper deformation (protuberance) in the reverse side of the print

LITHOGRAPHY

A printing technique, in which printing and spacing elements are located almost in the same plane. The inks are transferred to the substrate directly from the printing plate. Printing and spacing elements are separated due to different physicochemical properties: the printing element of the plate takes the form of the ink but repels water, while spacing elements receive water, get moistened and repel water (fig. 1).

The characteristic features of the prints:

• absence of relief;
• even saturation and density of the ink along the surface;
• slightly blurred contours, thin strokes are broken.

Fig. 1. Zoomed fragment of the background pattern printed by lithography. 10 Croatian Kuna (2004)

MAGNETIC INK

An ink containing ferromagnetic components, which have a specific reaction to the external magnetic field. The components can be added to the ink of any colour or colourless varnishes. The texts or images printed by the ink can be identified by special magnetic sensors or visualized by special devices.

The magnetic ink may be used on security threads, fibers, for printing serial numbers, texts and images. (fig. 1).

a	b
c	d

Fig. 1. Visualization of ferromagnetic components:
a – local distribution of texts and images. 100 USA Dollars (2006); b – fibers. 5 000 Russian Rubles (1997);
c – security thread. 2 000 Chilean Pesos (2009).; d – bar-code. 20 East Caribbean Dollars (1993).
Images are available in the Forensic version of the Database

METAL COATED IMAGE

An image on the banknote with a distinctive metallic glitter (not printed by an ink). Glitter intensity changes when changing the angle of view. It may also have additional security features (e.g. microtext) (fig. 1).

See also metallic ink, metallic patch GOLDswitch

a	b
Fig. 1. Metal Coated Image. 50 Swiss Francs, 8th Series (2004): a – view at right angles; b – view at an acute angle

METALLIC EFFECT METALIX

An ink containing pigments with a high index of refraction which reflect incident light and produce metallic sheen. It was developed by Innovia Security company for banknotes on the Guardian polymer substrate. As a rule, the Metalix ink is used to produce spot printed image elements. Metallic effect is viewed in reflected light on both sides of the banknote provided that the observation and illumination angles relative to the perpendicular are equal. Unlike the GOLDswitch element, Metalix color range includes red, gold, copper, silver, blue, green, violet and salmon.

Observation and illumination of Metalix element. Scheme: intense sheen is observed when the angles of illumination and observation are equal

a

b

c	d	e
20 Polish Zlotych (2014): a — front side of the banknote. Guardian polymer substrate; b — reverse side of the banknote. Guardian polymer substrate; c — spot printed image elements executed in gold and blue Metalix ink. Both observation and illumination angles are 0 degrees; d — ink pigments viewed in reflected light; e — the same image viewed in transmitted light

METALLIC INK

An ink containing metallic pigments of bronze and aluminum. It has a specific metallic glitter. Unlike optically variable ink, when changing the angle of view, while looking at the image applied by metallic ink, glitter intensity changes only. The colour does not change (fig. 1).

Fig. 1. Zoomed fragment of the image printed with the metallic ink. 50 000 Zambian Kwacha (2006)

METALLIC PATCH GOLDswitch

A metallic pigment that is made up as an ink and is printed on top of the polymer substrate as a patch. It has a metallic glitter. When changing the angle of view, glitter intensity changes, but not the colour (fig. 1). This patch may then be used as a platform for other security features such as intaglio contrast effect (ICE) and transparent intaglio disappearing effect (TIED).

Similar to metallic ink on the paper substrate.

a	b
Fig. 1. Metallic Patch GOLDswitch. 20 Brunei Dollars (2007): a – view at right angles; b – view at an acute angle

MICROPERFORATION

A security feature, consisting of micro holes made by laser and forming an image seen in transmitted light (the holes look like bright spots) (fig. 1). The area of the banknote with the holes does not feel rough to the touch.

Fig. 1. Microperforation. 200 Swiss Francs (1996)

MICROPRINTING

A printed image (usually repeated words, numbers of texts) 0,15–0,3 mm high. It is visible only with magnifying devices; can be perceived with the naked eye as a thin continuous line.

Classification

• positive microprinting consists of dark letters on a light background (fig. 1, a);
• negative microprinting consists of light letters on a dark background(fig. 1, b);
• reversed (turned out) microprinting changes gradually from negative to positive and vise versa. (fig. 1, c).

a	b
c
Fig. 1. Microprinting: a – positive. 10 000 Belarusian Rubles (2000); b – negative. 10 000 Belarusian Rubles (2000); c – reversed. 1 000 Russian Rubles (1997). Modification 2010

MOIRE VARIABLE IMAGE (MVC, MVC+)

MVC – Moire VariableColor

An effect of rainbow image appearance. Differently colored parallel lines are printed by offset before blind embossing. If viewed directly at right angles, the element looks monophonic (fig. 1, a). If the banknote is tilted, rainbow stripes appear (fig. 1, b).

MVC+ is an improved version of MVC. It contains two zones, if viewed directly at right angles. The rainbow can be seen in one zone, and one-colour background in the other (fig. 2, a). But if it is viewed at a sharp angle, the rainbow stripes appear in the space of the background and perfect registration among rainbow stripes in both zones can be seen (fig. 2, b). When MVC+ is viewed under UV light, the upper part of the area has one-coloured luminescence. When the banknote is tilted, luminescent different-colour stripes appear in the upper part of the area as a continuation of constantly visible stripes in the lower part.

a	b	a	b
Fig. 1. MVC. 5 000 Russian Rubles (1997).		Fig. 2. MVC+. 1 000 Russian Rubles (1997). Modification 2010.
a – views at right angles; b – views of the tilted banknote

OFFSET

A printing technique, which employs a plate with printing and spacing elements in the same plane. The inked image is transferred (or “offset”) from the plate to a rubber blanket, then to the printing surface.

Traditional offset is based on the repulsion of oil and water, the image to be printed obtains ink from ink rollers, while the non-printing area attracts water, keeping the non-printing areas ink-free. The plates are dampened with water which adheres to the areas without images. The ink is added next, one color at a time, where it sticks to the areas with images.

Characteristic features of the prints:

• the substrate is not deformed;
• the paint strokes evenly distributed;
• the paint does not shine (fig. 1, a);
• the paper fibers can be seen through the strokes (fig. 1, b).

High offset is a method which combines letterpress and offset. The image is transferred to a rubber blanket from a plate with the printing elements raised above spacing elements. Printing pressure is lower than that in letterpress, and the plate does not contact the substrate, so there is no relief. The prints obtained by this method are characterized by more distinct boundaries than offset prints. Relief printing elements on a printed plate lead to the same boundary effects, as in letterpress, but it appears to a lesser extent.

a	b
Fig. 1. Offset Printing. 5 Yuan Renminbi (1980): a – general view; b – zoomed fragment

OMRON RINGS

An image consisting of rings of the same diameter (about 1 mm) printed by offset. They form a certain structure composed of five Omron rings, one of which is the Eurion constellation. The rings are geometrical marks used for copy protection (fig. 1).

Fig. 1. Omron Rings. 500 Euro (2002)

ONE-SIDED WINDOW VIEWSAFE

An area in the form of a window one side of which is opacified on the front or reverse side of the banknote. On paper or hybrid substrate banknotes, it is made using a transparent film. One-sided window Viewsafe can be round shaped or any other complex shape.

Structure scheme of one-sided window Viewsafe for banknotes on paper or hybrid substrate

a	b	c	d	e
25 Moroccan Dirhams (2012): a — front side of the banknote, location of half windows; b — reverse side of the banknote; c — Viewsafe™ window developed by Landquart company. The watermark is overlaid with a transparent film; d — half window with a complex shaped overlay through which a security thread is visible; e — an overlay made of a transparent film, zoomed fragment

OPTICALLY VARIABLE DEVICE LATITUDE

A double-sided holographic image, located in the clear window of the polymer banknote. The element is being formed during the manufacturing process of the polymer substrate. The changing effect of the image colours appears when looking at the image at different angles of view (fig. 1).

a	b	c
Fig. 1. Optically variable device Latitude. 20 Polish Zlotych (2014): a – front side of the banknote; b, c – view at different angles of illumination and observation.

OPTICALLY VARIABLE ELEMENT WITH A POLYCHROME EFFECT AURORA

An optically variable security element with a multiple colour switching effect. It was developed by Innovia Security company as a further development of the G-Switch® element. It is applied during the formation of the Guardian substrate on one of its inner layers in the form of an image (picture or alphanumeric characters). A pair of image elements that work in combination appear as one colour at certain observation conditions, then a totally different colour at other observation conditions. Ink pigments which are semi-transparent in transmitted light have a pearlescent sheen in reflected light. The effect of a colour switch is observed both on front and reverse side of the banknote if the element is located on a clear window.

Scheme of observation and illumination: a pair of images С and С’ are of the same colour at an illumination angle of 0±10 degrees and observation angle of 45 degrees to the perpendicular; the colours of the images are different at an illumination angle of 0±10 degrees and observation angle of 0±10 degrees to the perpendicular

a

b

c

d

e

f

g

h

1000 Mauritanian Ouguiya (2014). Guardian polymer substrate: a — front side, Aurora element location; b — Aurora element viewed in transmitted light; c — the same image viewed in reflected light at an angle of 45 degrees. The pair of image elements (left and right) have a similar colour; d — the same image viewed at an angle of 0 degrees: the left element is golden and the right element is blue; e, f — the same image viewed in transmitted light; g — ink pigments viewed in reflected light; h — the same image viewed in transmitted light

OPTICALLY VARIABLE ELEMENT WITH COLOUR SHIFTING EFFECT SWING

A pair of images which change their colour depending on illumination type. The element is printed on polymer substrate with iridescent ink containing liquid crystals. The colour of the images does not change in reflected light at different angles of illumination and observation. The colour shifting effect in the two images is observed in transmitted light: their colours are reversed.

a	b
Observation of colour shifting (changing) effect. Scheme: a — view in reflected light under front illumination: blue colour of the number “50” and yellow colour of the symbols “RS”; b — view in transmitted light: yellow colour of the number “50” and blue colour of the symbols “RS”

a	b	c	d	e
Optically variable ink with colour shifting effect SWING. 50 Mauritius Rupees (2013): a — front side of the banknote, clear window with the SWING element; b — SWING element, view in reflected light; c — the same image viewed in transmitted light; d — ink structure in reflected light (fragment of the number “5”); e — the same image viewed in transmitted light

OPTICALLY VARIABLE INK (OVI)

OVI – Optically Variable Ink

An ink, containing optically variable pigments which change colour depending on the angle of light incidence and view. Applied by intaglio or screen printing.

It is important for colours to be contrasting and well distinguishable (fig. 1).

a	b
Fig. 1. Optically Variable Ink (OVI). 500 Euro (2002): a – view at right angles; b – view at an acute angle

OPTICALLY VARIABLE INK WITH EMBOSSING

Integrated optically variable security element, which comprises:

1. optically variable ink;
2. blind embossing;

The result provide colour change effect when tilted, that is enhanced by a latent image produced by embossing which is not visible without tilting (fig. 1).

a	b	c
Fig. 1. Optically variable ink with blind embossing at different angles of view. 1 000 Mozambique Meticais (2006):  a – without tilting; b, c – tilted (different angles)

The element may also comprise of an iridescent ink patch, which provides an additional pearlescent sheen when the banknote is tilted (fig. 2).

a	b	c
Fig. 2. Optically variable ink with blind embossing and iridescent ink patch at different angles of view. 50 Bahamian Dollars (2006):  a – without tilting; b, c – tilted (different angles)

OPTICALLY VARIABLE INK WITH POLARIZING EFFECT

A semi-transparent optically variable ink containing liquid crystal pigments with polarizing properties. When viewed from different angles in white light the image usually printed by offset and covered with the ink changes colour (fig. 1). The polarizing properties are checked through a special polarizing filter consisting of two windows – the colour of the image differs (fig. 1).

a	b
c
Fig. 1. Optically variable ink with polarizing effect. 50 000 Armenian Drams (2001): a – without tilting; b – tilted; c – view through a polarizing filter

OPTICALLY VARIABLE MAGNETIC INK (SPARK, OVMI)

OVMI – Optically Variable Magnetic Ink

A multi-level (visual and machine readable) security feature. The visual effects are based on the magnetic properties of an optically variable magnetic ink. The ink contains a special magnetic pigment located with the help of magnetic fields within the ink layer. When the banknote is tilted, there is a combination of the colour changing effect and (unlike optically variable ink) the dynamic effect of the ink movement (bright parts of the image “change” places). Usually printed by screen printing (fig. 1).

a	b	c
Fig. 1. Optically variable magnetic ink. 50 000 Uganda Shillings (2010): a – at right angles; b, c – different acute angles

OPTICALLY VARIABLE PATCH Jasper

Integrated optically variable security element, which comprises:

1. hologram;
2. blind embossing.

The result provide holographic effect when tilted, that is enhanced by a latent image produced by embossing which is not visible without tilting (fig. 1).

a	b	c
Fig. 1. Optically variable patch Jasper. 10 Libyan Dinars (2011):  a – without tilting; b – tilted; c – zoomed area of the element showing blind embossing

OPTIKS WINDOW

A complex security feature, which consists of:

1. a hidden wide security thread (up to 18 mm), inserted into the paper during its manufacturing process and seen in transmitted light;
2. a hole in the paper substrate with uneven edges and fibers along its perimeter forming a kind of fringe;
3. a transparent polymer strip with metallized coating covering the hole on the front or back side (fig. 1).

a	b	c	d
Fig. 1. Optiks window. 100 Pa’anga of Tonga (2008): a – thread under reflected light; b – thread in transmitted light; c – window; d – zoomed edge of the window

ORLOV EFFECT

A method of multi-color printing, in which:

1. the composition form picks up the ink from multiple line block plates;
2. the colours are transferred to the banknote substrate in one rotation.

The print is characterized by perfect registration of colours without breaking and shifting (fig. 1).

Fig. 1. Orlov effect. 5 000 Belarusian Rubles (2000)

PLANCHETTES

Thin round or polyhedral pieces 1–4 mm in size made of polymer (paper) (fig. 1, a, fig. 2). They are incorporated in the paper during the manufacturing process or pressed to its surface layer. They are distributed randomly or as a strip in a certain place of the banknote. Planchettes can be coloured and luminescent under UV light (fig. 1, b). Moreover, planchettes with high reflection power (“blinking”, “anti-copy”) prevent image formation by copiers (fig. 2).

a	b
Fig. 1. Round planchettes. 100 Canadian Dollars (1986): a – view under white; b – view under UV light (365 nm)		Fig. 2. Hexahedron Planchettes with iridescent coating. 10 Soles of Peru (2001)

POLE FEATURE

A security feature based on the phenomenon of light polarization. It is a liquid crystal coating, which reveals polarizing properties, when viewed through a polarization filter (an image may appear or disappear) (fig. 1).

a	b
Fig. 1. Pole feature. 5 000 Russian Rubles (1997): a – white light without filter; b – view through the polarization filter

RAINBOW PRINTING

A printing technique, in which two or more inks are applied on one printing plate. During the printing process, the inks are mixed, which results in the formation of intervening tints with smooth colour transitions among the main colours of the image, avoiding breaks and displacements (fig. 1).

Fig. 1. Rainbow printing on the background pattern. 1 000 Belarusian Rubles (2000)

SCREEN PRINTING

A printing technique, which enables to obtain an image by pushing the ink through the printing plate. The printing form is a frame with a stretched silk or nylon gauze on it. The image is transferred to the gauze by means of a photographic process. A wiping blade, called a squeegee, pushes the thick ink through the gauze and creates a printed image. The spacing elements are covered with a layer, which does not let the ink. The printing elements are open (fig. 1).

Characteristics of a print:

• the subsrate is not deformed;
• a thick ink layer;
• zigzag edges of the image;
• the mesh structure of the image;
• absence of thin strokes.

a	b
Fig. 1. Image printed by Screen printing. 10 000 Kazakhstan Tenge (2011): a – general view; b – zoomed fragment of the image

SECURITY FIBERS

Fine coloured or colourless fibres located randomly in the paper substrate or on its surface. Fibres are incorporated into the paper during its manufacturing process and are distributed among other fibres of the paper pulp.

Classification

Perception degree with the naked eye:

• visible security fibres which do not luminesce under UV, IR and other lights and may have magnetic properties;
• visible security fibres which luminesce under UV, IR and other lights and may have magnetic properties (fig. 1);
• invisible (transparent) security fibres which luminesce under UV, IR and other lights and may have magnetic properties (fig. 2).

Fig. 1. Visible under white reflected light. 20 000 Lebanese Pounds (2004)

Fig. 2. Invisible under white light. Luminescence under UV light (365 nm). 50 Ukrainian Hryven (2004)

Colouring:

• coloured security fibres;
• colourless security fibres;
• security fibres with alternate areas of different colours.

Fibre structure:

• simple security fibres;
• security fibres with variable cross-section of the profile (fig. 3).

a	b
Fig. 3. Security Fibers with variable cross-section. Zoomed image. 1 000 Russian Rubles (1997). Modification 2010:  a – under white reflected light; b – under UV light (365 nm)

SECURITY THREAD

For the banknotes on the paper basis:

A narrow strip on the polymer basis incorporated into the paper substrate during the manufacturing process of the paper.

Classification

Location in the paper:

• latent (solid) security thread is located completely in the paper and can be seen in transmitted light only (fig. 1);
• diving (window) security thread can be seen on the paper surface as rectangles which form a dot line on the banknote surface and a solid line when viewed against light (fig. 2);
• figured security thread appears partially on the paper surface as a figured window and as a solid strip when viewed against light (fig. 3).

a	b	a	b	a	b
Fig. 1. Latent. 2 000 Iceland Kronur (1986)		Fig. 2. Window. 50 Swaziland Emalangeni (1995)		Fig. 3. Figured. 1 000 Russian Rubles (1997). Modification 2010
a – reflected light; b – transmitted light

Materials and security features:

• metallized without texts (fig. 4, a);
• metallized with microtext applied by demetalization (fig. 4, b);
• semi-transparent with texts (fig. 5);
• holographic (fig. 6);
• colour-changing (fig. 7);

a	b			a	b
Fig. 4. Metallized. Transmitted light: a – without texts. 2 000 Iceland Kronur (1986); b – with microtext. 50 Swaziland Emalangeni (1995)		Fig. 5. Semi- transparent with microtext. Transmitted light. 10 UAE Dirhams (1982)	Fig. 6. Holographic. Reflected light. 200 Nigerian Naira (2000)	Fig. 7. Colour changing. 50 Libyan Dinars (2008): a – at right angles; b – at an acute angle

• luminescent under UV light;
• with magnetic properties;
• with the “floating” Motion image: when inclining the banknote, the images on the security thread are moving perpendicular to the direction of inclination (fig. 8);
• with the optically variable effect “Scate”: the image disappears from the security thread at a certain angle of view and leaves iridescent tints of the hologram (fig. 9);

a	b	a	b
Fig. 8. Motion effect. 100 000 Lebanese Pounds (2011)		Fig. 9. Optically variable effect “scate”. 500 Russian Rubles (1997). Modification (2010)
a – at right angles; b – at an acute angle

• with the optically variable effect “Chameleon”: the images applied on the security thread look positive under reflected light and negative in transmitted light (fig. 10);
• with the kinetic effect “Mobile”: when changing the angle of view, certain images shift relative to each other (fig. 11).

a	b
Fig. 10. Optically variable effect “Chameleon”. 1 000 Russian Rubles (1997). Modification 2010: a – under reflected light; b – in transmitted light		Fig. 11. Kinetic effect “Mobile”. 5 000 Russian Rubles (1997). Modification 2010: at different acute angles

For banknotes on the polymer basis

An image in the form of a narrow dark or light semi-transparent strip printed on the surface of the polymer substrate.

It may contain microprinting, special inks with magnetic properties and other security features (fig. 12, fig. 13).

a	b	a	b
Fig. 12. Dark thread without microtext. 20 Dominican Pesos (2009)		Fig. 13. Light thread with microtext. 10 Taka of Bangladesh (2000)
a – transmitted light; b – zoomed image in transmitted light

SEE-THROUGH REGISTER

An image, a part of which is printed on one side of a banknote and the other part on the other side of a banknote. When the banknote is viewed against light, both parts match up and create a complete image. This can only be carried out on a simultaneous press and cannot be done on printing equipment used in usual polygraphy.

The image should not have any gaps or shifts and can only be seen in transmitted light (fig. 1, a–c).

a	b	c
Fig. 1. See-through register. 200 Romanian Lei (2005): a – front side; b – back side; с – in transmitted light (from the front side)

SELF-VERIFYING FILTER

A clear window with a filter (coating) which can visualize latent images or texts located on the same banknote. When bending the notes, the filter is placed over the area containing such an image (fig. 1, c), which changes colour and becomes visible (fig. 1, b).

a	b	c
Fig. 1. Self–verifying filter. 10 Brazilian Reals (2000): a – image without filters; b – through the filter; с – verification process

SERIAL NUMBER

The unique combination of letters and (or) numbers, which is assigned to each banknote. It is usually printed by letterpress. UV, Infrared, and magnetic inks can be used to print serial numbers. Information about a year of issue and series, an issuing bank, a factory, a face value, etc. may be encoded in serial numbers (fig. 1).

Fig. 1. Multicoloured serial number. 50 Pounds Sterling (2010)

SHADOW IMAGE

A tonal image seen in transmitted light; produced by altering the opacity or the colour of a polymer substrate layer. The element is similar to a watermark in thecotton-paper banknote.

CLASSIFICATION

Depends on the location on a banknote:

• local is a shadow image located in a particular area of a banknote (fig. 1, a);
• strip is shadow images located one above another in a particular area of a banknote (fig. 1, b).

a

b

Fig. 1. Shadow image. Transmitted light: a – local. 20 New Israeli Sheqalim (2008); b – strip. 20 Honduras Lempiras (2008)

Depends on the tone gradation:

• single-tone – consists of darker (or lighter) elements compared to the general tone (fig. 2, a);
• duotone – consist of darker and lighter elements (fig. 2, b);
• multi-tone (half-atone) – an image with gradual transitions between darker and lighter areas (fig. 2, c).

a	b	c
Fig. 2. Tone gradation of the shadow images: a – single tone. 5 Brunei Dollars (2002); b – duotone. 20 Honduras Lempiras (2008); c – multi-tone. 20 New Israeli Sheqalim (2008)

SUBSTRATE

Substrate is a special material used to produce banknotes.

Paper substrate is a thin material consisting of plant fibers (cotton, linen etc.).

Polymer substrate is a thin (approximately 0.1 mm) clear plastic film covered with multiple layers of specialized coatings.

Hybrid substrate is a material consisting of paper and polymer layers.

THERMAL INK

An ink which changes its colour or optical density, when the image is exposed to heat. The images may change colour, become visualized or decolourized. Usually reversible thermal inks are used, which return the initial colour after heat exposure (fig. 1).

a	b
Fig. 1. Thermal Ink. 500 Latvian Lats (2008): a – general view; b – decolourization of the image after its exposure to heat

TRANSPARENT INTAGLIO DISAPPEARING EFFECT TIED

TIED – Transparent Intaglio Disappearing Effect

A combined security feature consisting of an image printed by intaglio onto the reflective metallic gold (or silver) patch. This combination creates a disappearing effect as the intaglio print is only visible at the angles of view, where the background is of high reflection. (fig. 1, b)

a	b
Fig. 1. TIED. 20 Singapore Dollars (2007): a – view at right angles; b – at an acute angle

UV-FLUORESCENT HI-LITES

Small coloured or colourless particles embedded in the paper during the manufacturing process. The particles glow when exposed to UV light (fig. 1).

a
b	c
Fig. 1. UV-fluorescent hi-lites. 5 000 Costa Rican Colones (2005): a – Hi-lites glowing under UV light; b – zoomed image under white light; c – zoomed image under UV light

UV-FLUORESCENT INK

Ink containing fluorescent substances (pigments) which glows when exposed to UV light (wavelength is usually of 365 nm and 254 nm). The pigments are not visible under normal daylight, only under UV light. The same pigment may have different sensitivity to UV radiation of different spectral ranges. The ink may be used for printing certain graphic elements and general patterns of the banknotes. Security fibers, planchettes, security threads, serial numbers can also fluoresce under UV light (fig. 1).

a
b
Fig. 1. Fluorescence of the security thread, security fibers, serial number, images invisible under white light in UV light. 500 Nicaraguan Cordobas Oro (2007):  a – under white light; b – under UV light

VARIFEYE WINDOW

A hole in the paper covered by a transparent film (with liquid-crystal or other coatings) from one side of a banknote. Design features within the Varifeye change in contrast as a banknote is moved over a black or white background. There may also be a kinetic affect. The feature is produced during the manufacturing process of the paper substrate and has fibers forming a kind of fringe along the perimeter of the hole (fig. 1).

a	b
Fig. 1. Varifeye. 20 Bulgarian Leva (2005): a – against the dark background; b – against the light background

VARNISH COATING

A security feature consisting of two varnishes: matt and glossy. Images (texts) are printed by glossy varnish over matt varnish and are visualized, when the banknote is tilted due to the contrast of the varnishes. (fig. 1, b).

a

b

Fig. 1. Fragment of the front side of the banknote with Securicoat. 50 Nigerian Naira (2010): a – at right angles; b – at an acute angle

WATERMARK

An image visible in transmitted light only, incorporated into the paper during its manufacturing process. A watermark has slightly diffused blurred contours and gradual transitions of the tones. It is formed by the density of the fibres on certain areas of the image. Thus, darker elements of the watermark are located on more dense areas of the paper, and lighter elements are located on less dense areas. The watermark does not appear under UV light.

Classification

Location:

• General watermark is an image repeated all over the banknote (fig. 1);
• Local watermark is an image located in a specific place of the banknote (fig. 2);

Fig. 1. General. 500 Cambodian Riel (1996)

Fig. 2. Local. 1 000 Belarusian Rubles (2000). Modification 2011

• Strip watermark is a band of images repeated one above another; is located in a specific place of the banknote (fig. 3);
• Cornerstone watermark consists of several parallel diagonal lines located in the banknote corners (designed to physically strengthen the corners (and edges) of banknotes) (fig. 4).

Fig. 3. Strip watermark.. 100 Norwegian Kroner VII series (1995–2002)

Fig. 4. Cornerstone watermark. 1 Libyan Dinar (2009)

General paper tone:

• Single tone watermark consists of darker (or lighter) elements compared to the general paper tone (fig. 5);
• Duotone watermark consist of darker and lighter elements compared to the general paper tone (fig. 6);
• Halftone watermark is an image with gradual transitions between darker and lighter areas (fig. 7);

Fig. 5. Single tone. 10 Belarusian Rubles (2000)

Fig. 6. Duotone. 500 Cambodian Riel (2004)

Fig. 7. Halftone. 20 Belarusian Rubles (2000)

• Pixel watermark is formed by dark dots on the light background (fig. 8);
• Highlight watermark (electrotype) is an extremely light clear single tone watermark with clear boundaries (fig. 9);
• Combined watermark combines several kinds of watermarks (fig. 10);
• Coded watermark consists of dark and light vertical strips located on the printed area of the banknote (is used as a machine-readable feature) (fig. 11).

Fig. 8. Pixel. 1 000 Kazakh Tenge (2011)

Fig. 9. Highlight. 1 000 Czech Korun (2008)

Fig. 10. Combined (halftone and highlight). 50 Gibraltar Pounds (2010)

Fig. 11. Coded. 500 Euro (2002)

WINBOSS EMBOSSING

An image (usually a banknote denomination) which appears in the transparent window produced by colourless embossing. It can be seen both under reflected and transmitted light. The element combines tactile and visual characteristics. (fig. 1, a).

а	b
Fig. 1. WinBoss Embossing. 50 Australian Dollars (2006): a – reflected light; b – transmitted light

WINVU FEATURE

A vignette design feature placed in the transparent window that adds both aesthetic and security dimensions to the banknote. The opacity of the window is adjusted to achieve distinctive designs. This feature is printed by gravure printing on the polymer substrate (fig. 1). It can be combined with a half window and a shadow image.

Fig. 1. WinVU feature. 500 Brunei Dollars (2006)