Saturday, December 21, 2019

How Secure is Our Currency? Understanding Security Features in Currency Notes


Dr. Bhoopesh Kumar Sharma
Forensic Expert & Associate Professor

Declaration: All images used in this article are from google sources, and only intended for the educational purposes. None of them is intended for any other purpose and should not be used by anybody other than educational (teaching and learning) purposes. Thanks.

What are Banknotes:

A banknote is a promissory note issued by a bank and payable on demand to the issuer. The sum payable is shown on the note's face. Banknotes are considered legal tender and form the bearer types of all modern money together with coins. Often referred to as a "bill" or "note."

Types of Bank Notes

1. Paper Notes
2. Polymer Notes
3. Others: Silk & Leather

Paper banknotes:

They are made from cotton paper with a weight of 80 to 90 grams per square meter. The cotton is sometimes mixed with linen, abaca, or other textile fibers. Generally, the paper used is different from ordinary paper: it is much more resilient, resists wear and tear also do not contain the usual agents that make ordinary paper glow slightly under ultraviolet light. Unlike most printing and writing paper, banknote paper is infused with polyvinyl alcohol or gelatin, instead of water, to give it extra strength. 

Most banknotes are made using the mold making process in which a watermark and thread are incorporated during the paper forming process. The thread is a simple looking security component found in most banknotes. It is however, often rather involved in construction comprising fluorescent, magnetic, metallic, and micro print elements. By combining it with watermarking technology, the thread can be made to surface periodically on one side only. This is known as windowed thread and further increases the counterfeit resistance of the banknote paper.

Polymer banknotes 

They are made from a polymer such as biaxially oriented polypropylene (BOPP). Such notes incorporate many security features not available in paper banknotes, including the use of metameric inks. The BOPP substrate is processed through the following steps:
Opacifying – two layers of ink (usually opaque white) are applied to each side of the note, except for any areas deliberately left clear;
Sheeting – polymer substrate roll is cut into sheets to suit a flat sheet printing press;
Printing – traditional offset, intaglio, and letterpress printing processes are used; and
Overcoating – notes are coated with a protective varnish.

Security Levels of Polymer banknotes:

Primary security devices are easily recognizable by consumers: include intaglio, metal strips, and the clear areas of the banknote. 
Secondary security devices are detectable by a machine. 
Tertiary security devices may only be detectable by the issuing authority when a banknote is returned.

  • Polymer Substrate.
  • Security Thread
  • Watermarks
  • Holograms
  • Clear Window. 
  • See-through Registration Device
  • Shadow Image
  • Intaglio Print
  • Background Print (offset) 
  • Microprinting
  • Fluorescent Ink
An Image of 1000 Dirham Note Showing Various Security Features 

Examination of Security Features of currency Notes:

The examination of the various security features in a suspected (counterfeit currency) can be grouped into the following categories: 

A.Physical Dimensions
B. Security Features in Currency Note Paper 
C. Security Features in Currency Note Printing 
D. Security Features in Currency Note Design elements
E. Other features, if any 

The comparison of features mentioned above has to be done with sample notes of same design and denomination available in the data bank of laboratory

Physical Dimension: 
The cut size of the note is studied in the form of length, width, and a grammage of paper and thickness of the paper/substrate and compared with that of authentic currency/ banknote. 

Security Features in Currency Note Paper: 

The currency notes are printed on high-quality paper made of 100% cotton. The cotton is used because of its unique features like natural whiteness and length of fiber and folding strength due to which the currency notes have a surface finish and crackle. The following features of the currency note, in the order listed below, are to be examined, and observed values are to be recorded. 

Unique feel, crackling sound and finish Raw material – cotton pulp or wood pulp Colour of paper, Opacity, Transparency 

Watermarks: Multi-tonal Portrait,  Other watermarks 

UV/ optical fibers
Colour of fluorescent 
Number of colours
Wavelength of fluorescence 
Density-Numbers per Square inch and Length of fibers 

Security thread 
Present / Absent 
(If present: Continuous / discontinuous Windowed / Embedded / Printed No. of Windows 
Ladder watermarks 
Width of thread 
Text (Micro text Present or Absent)
Height of the clear micro text
Content – (Material – Metallic/ polyester/ metal coated polyester/ 
fluorescent non-fluorescent.
Readable from front/back
Magnetic/ non-magnetic 
Colour(s) of fluorescence Wavelength of fluorescence Position Floating / Stationary 

Printing Ink 
Fluorescence : (UV Wavelength 254 and 365 nm)
OVI - Optical variability of colour– shift effect
(OVI printing by Intaglio screen printing) 


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