Ultraviolet Light and Black Light: a beginner's guide

1) Introduction

2) What is ultraviolet light?

3) The different kinds of UV light

4) Your tool for this guide: a black light

5) Where does ultraviolet light come from? How was it discovered? Why can't we see it?

6) How are black lights made?

7) Practical and interesting uses for your black light

8) Examining art and collectibles: Introduction

9) Identifying modern fakes of antique paper memorabilia

10) Identifying counterfeit US currency

11) Identifying alterations to art, collectibles

12) Examining cloth

13) Examining art glass

14) Making glow in the dark art and crafts

15) Protecting yourself from the Sun's UV

16) UV light in science and industry 

Identifying Counterfeit US Currency

The are numerous methods used for identifying counterfeit US currency bills, including the use of black light. Note that this section is only a brief and general introduction. Currency is regularly changed and updated by the US Government, and it's likely that there will be new changes within a few years or less of the publication of this guide. Newly issued currency doesn't make old currency totally disappear. Old currency is floating around for many years. If you find a 1930 $1 bill it's valid currency.

Counterfeits vary in quality, from easily identifiable to sophisticated. The following techniques will help identify most counterfeits.
The following looks at specific techniques of counterfeit detection. An important thing to realize is that a single correct quality does not prove a bill authentic. For example, some counterfeiters bleach genuine $1 bills and make them into fake $20 bills. That the paper itself is genuine doesn't prove these fakes authentic.

Pay attention to your currency
Observe your bills before you get counterfeits. Look at the printing, the Presidential portrait, examine the details, get a feel for the paper. A common way a counterfeit bill is found suspect is that it looks and feels off, different from other bills. The image may look funny and unclear, the color may be off, the paper may feel different.

Real bills have high quality, detailed printing. Check the details and lines in the portrait and in the background lines. The detail in reprints is often lacking and muddled.


Compare a suspect bill to known genuine bill of same denomination and year. Again compare the feel and general look. Compare specific, close up details, like the President's eye or the points on a seal. Compare all the designs and text. Again, remember that the design and text changed over the years on genuine bills, so you want to compare bills from the same year.

Take into consideration that there can be natural differences between genuine bills. One genuine bill can be crisp and unused, while another genuine bill can be worn, wrinkled and dirty. This is why comparing to numerous bills is a good idea.

Black light test #1: fluorescent vertical bands.
Some recent currency above the $1 denomination has vertical bands that fluoresce under black light. Under normal visible light, the bands can be seen when the bill is held up to a light. The presence of these is strong evidence of authenticity.

Florescence of bands:

$100 Pink/Orange
$50 Yellow
$20 Green
$10 Red
$5 Blue


Black light test #2:
Authentic currency does not have optical brighteners in the paper. Many, but not all, counterfeits are made with normal paper and will fluoresce brightly.


Watermarks. Modern higher currency bills have a watermark to the side of the bill. The authentic watermark is not seen until it is held up to a light. It will be a smaller portrait of the president on the bill and can be seen when viewing from both sides.

2006 US$ bill with watermark. The left is the normal, everyday view. On the right, the bill was held up to sunlight revealing a watermark. If $5 bills are bleached and printed over to make higher denomination ($20, $50, other), the '5' watermark will identify them as fakes. Many bills, including this one, have watermarks of the President on the bill. Again this will help identify bleached counterfeits. An Abe Lincoln watermark shouldn't appear on a Andrew Jackson biil.


Fibers in paper. Some modern currencies have thread-like fibers of different colors in the paper. Some counterfeits will look like they have the threads, but close examination under a microscope or high magnification shows the fibers real on a real currency.

colored fibers can be seen in the paper



Microprinting: Microprinting is very, very small text that appears in some parts of some but not all currency. It is readable under magnification and very hard to reproduce in a counterfeit. In most counterfeits, the microprinting will be all blurred under magnification.


Color shifting ink on higher than $5 currency: On modern higher currency, there is a distinct color shifting ink used on the front right. It has a metalicy finish and is used on two right simbols. It changes color, from green to black, when you change the angle of the bill. This is hard to duplicate in counterfeits.


Minute multi-color dot pattern as identifier of counterfeits. When you examine a genuine bill under good magnification, you will see the images, writing and design are comprised of solid monotone lines and marks. Some, but not all, counterfeits are identified by a minute mult-color dot pattern in the printing. Many digital computer prints will have this pattern.

Raised notes. Some genuine notes are altered to give them a high denomination. For example, a forger may take a $1 bill and past '$10' on the corners. This is identifying by knowing which presidents appear on which bills. George Washington appears only on a $1. Also, the correct denomination is spelled out just below the President's portrait.

Paper testing pen. There are inexpensive commercially available pens that test the paper. Genuine currency is fiber based, while some counterfeits are on wood based paper. Common computer paper is wood-based. The pen contains iodine that makes a black stain on wood-based paper, but not on fiber-based. The black stain shows that the bill is counterfeit. Realize that some counterfeits are made on fiber-based paper, including bleached genuine currency, so the pen won't identify all counterfeits. Many foreign currencies are on fiber based paper, so the pen will work with the European Euro. Mexican Peso, Brazilian Cruzeiro, Argentine Peso, Indian Rupee, Greek Drachma, German Mark, French Franc, British Pound, Italian Lire, Russian Ruble, Japanese Yen and numerous other paper currency.


11) Identifying alterations to art, collectibles

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