The most important problem in the life of the modern banknotes is providing the banknotes with the up-to-date security features. Counterfeiting is reaching the history highest amounts, and developing the more and more advanced ways of protecting the national cash currency is the task most governments of the world countries face.

How can you decide whether the banknote you hold in your hands is authentic or a bad fake ? As usual, most of us will look for the banknotes' watermark, will try to feel the quality of printing with our fingertips and, perhaps, will search for a mystic security thread we once heard about but never noticed before.

Is that enough ? Perhaps, it is for the regular checking, but not for an in-depth analysis, of course. How many security features do you know ? 5 ? 10 ? A dozen ? Anyway, that's not all, there are more than thirty in total ! Here are some of the most widely used in modern money issuing industry: (click to see a brief description of each):

The banknotes are usually made of the special kinds of paper, which are very different from what we use to write our letters on. The purpose is to provide the longer life cycle of the note and make it harder to counterfeit. Normally, special kinds of flax and / or cotton are added to the cellulose when banknote paper is produced. Each banknote should have fair resistance to water and wear, at least 2000 folds should be made before torns appear.

Didn't you ever notice that the banknotes (especially not worn) make very specific sound, or "crisps", when being folded ? Just give it a try and compare with the ordinary paper sounds. Felt the difference ? Hope so.

Watermarks are among the most popular and well-known security features of paper money. The process of making a watermark is very complicated and involves many stages when paper is made of raw and wet cellulose. In fact, the darker areas of a watermark are where the cellulose layer is thicker. There are 2 common types of watermarks: localized, for instance, a portrait - see in the middle (taken from DEM 100 banknote) and whole area marks, which cover the entire banknote - see the right pic (taken from 1000 pesos argentinos). Portraits are considered more reliable as a security feature as they contain more semi-shadows. It's also a good practice to have denomination on the watermark, like on the Russia banknotes of 1995-2001 (pic from 100.000 roubles 1995, in the left).

Security threads are among the most reliable features, which are extremely difficult to be made without specialized equipment. These are embedded into the paper when the banknote is yet being made of raw cellulose. There are 2 common types of threads: internal and diving. Internal ones are completely inside the paper sheet; they may be solid (left pic, from DKK 500) and may be transparent, containing micro-inscriprions. They can be made of metal and plastic. The diving threads are usually made of foil, and you can often see it glittering on the face sides of the banknotes. Usually these threads have text in them, which can be seen against the light (middle and the right pics, from 10 kuna, Croatia and DEM 100).

An extremely difficult thing to counterfeit is the matching element. It's made as follows: 2 different pictures are printed simultaneously on the sides of the banknote, which are parts of one whole sign or symbol. Their location is so exact that when held against the light they form a perfectly matching drawing. It's nearly impossible to repeat when making plain copies of the banknotes. See the pics on the right: the first 2 are pics from both sides of the banknote (10 kuna, Croatia, in this case), and the third gives you an idea of what they form together (letter "H").

Kipp effect, or the latent image, is a relatively new feature added to the banknotes beginning with the 1980ies. It's made with the help of intaglio printing (see below). Usually the image is "hidden" in the areas of the same tone and it's built of raised parallel lines, which are perpendicular to the raised lines of the background. When you rotate such area with the light reflecting from it, at certain angles you will see the picture appearing and then changing into negative. The pic shows how it looks like on the DEM 100 banknote.

"Intaglio" means "raised". It's one of the most interesting things about the modern banknotes, I think. The technology is rather complicated, but, in brief, it's developed to place about 60 layers of paint on the same place on the note and to apply the effort which equals 60 tons in weight. The letters (or drawings) thus acquire volume and you can feel them with your fingers. And at the same time it's applied so strongly that you can't scratch the paint off. On the left you can see the letters "Cla.." from the DEM 100 banknote, which are raised above the microtext.

One may find it strange, but the numbers on the banknote usually have relation to the security features, too. Each banknote's number is unique, and they never repeat. Usually the numbers depict the working place at the banknote factories where they are made. There are plenty number formats used in the world - some numbers have series in letters, some have not; some numbers may include 5 digits - the others may have 11. There are certain banknotes that have no numbers at all - like those coupon issues of Ukraine (early ones) and small Belarus roubles (first banknotes). The way of writing a number can be a security feature, too. The numerals can be increasing in size (like shown on a pic from EEK 50 banknote) or decreasing. The numbers are usually repeated twice on the banknote - in case you tear it, it will be easier to see which banknote was torn (for the purpose of it's utilization).

One of the most interesting features used with the modern banknotes. This looks like there is an imprint of some glittering sand on the banknote, and it changes it's colour when you view the banknote from a different angle. This effect is quite complicated: if you look at the banknote with a microscope, you'll see that this imprint consists of the raised poligonal objects. Their topmost sides have one colour, while the sides have another. When you change the angle, you stop viewing one colour, and it seems substituted by another. Exciting, isn't it ? (Pics: left - top view of the element on the turkish 500.000 lire note, middle - side view; right - Bosnian 50 feninga note, pale yellow strip changes into blue one)

For a certain reason signatures are often added to the banknotes. They belong to the head treasurers, Central Banks' chairmen of the boards of directors, general secretaries of those banks, etc. Some signatures are really difficult to reproduce, but... I wouldn't say it's a reliable feature; rather an element of the banks' obligation to pay the bearer on demand. (The pic: signatures from Argentina 50 australes banknote).

Many modern banknotes have the so called "metal dust" on them. That is a special kind of paint which has smallest metal particles in it that give the banknotes a unique metal glitter where applied. It's used for many purposes, sometimes in combination with other features like latent image or glowing in UV rays (see below). Russian 5 rouble banknote metal dust plated numeral on the pic.

A fascinating thing about the banknotes is the way they glow under UV rays. There are certain types of paint used which glow under these rays and show you the pictures you don't see under normal, sun lighting. Those can be the banknote's denomination, ornaments, coats of arms - whatever the fantasy allows. Besides that, the banknote paper itself has a very specific colour under UV: most banknotes' paper appears dark blue, sometimes with pink, while ordinary paper shines very bright blue. (The pic - DEM 100 banknote under UV rays)

"Hair" are small pieces of specially treated materials (silk as usual) added to the banknote paper when it's being made. Their task is to act as an additional security feature as they use to glow with different colour under the UV rays. The amount of such "hair" can be different from note to note, and they have no fixed location. Picture taken from Argentina 50 australes banknote.

Protection ornaments are normally used to prevent the volunteers add extra nulls to the denomination. the worst situation was in Georgia, when coupon banknotes were introduced. In half a year so many "corrected" banknotes appeared that the government had to issue new notes with this kind of security feature.

Marks for the blind are closely involved with intaglio printing as they are what the blind people can feel with their fingertips. Depending on the denomination, the "finger picture" will differ. However, there's a more advanced way to make life easier for the blind, like that was made in Canada. Canadian banknotes have magnetic marks (viewed as black marks on the reverse) and when installed in a special small reading machine, a voice tells the denomination. (Left pic: marks on the 100.000 roubles of Russia, 1995; right pic - from Canada $2 banknote).

Polymer banknotes are the most advanced banknotes of today. In several countries it was decided that polymer is a better substitute to the paper, and there were reasons for that. Plastic is far more resistant to wear than paper, it doesn't dissolve in water and doesn't burn. The average life term of polymer note is several years (unlike 8 months of a paper note). Besides, some security features of the polymer notes are unique - like the transparent windows in them (see the pic, taken from 2000 leu of Romania).

One of the most recent development among the security features, which is alike with the UV-glowing, is the IR-glowing (Infra Red). Some areas of the banknote are covered with the paint which makes the picture darker under the IR rays. To the moment I'm aware of only 2 currencies, using such feature. These are the russian rouble and the euro.