"Forgery" Return to list of pracs

Aim: This activity is used to look at discovering a forgery in detective work.

Chromatography to find a forged cheque:

Equipment: The equipment includes...  

• ink samples A and B;
• filter paper;
• dropper;
• scissors;
• a "fake" cheque;
• beaker of water.

Method: Cut a piece of filter paper as shown below:

Using a dropper, put a small drop of sample A on the paper in the centre and fold the flap so that it slopes downhill. Place the filter paper on top of the lid of beaker of water with the flap touching down onto the surface of the water. When coloured rings form, take the filter paper out and place on a piece of paer to dry out.

Do the same for sample B.

Background knowledge: When someone alters a signature or fugure on a cheque, he or she is a forger. Cheques may be forged by blotting out words or numbers and replacing them with others (eg. changing seven with seventy dollars). Chromatography allows you to identify the types of inks that are in the pen that was used. Inks are made of a mixture of syes. This process separates the dyes. Two inks that look the same may not come from the same pen. Chromatography is a method of separating the dyes.

Using UV light to show up forgeries:

Equipment: The equipment includes...  

• UV light;
• forged cheque..

Method: Place the forged cheque under a UV lamp which has been sheilded from normal outside light sources. Draw circles around the areas that show up as forgeries.

Background knowledge: When white light is shone through a triangular prism the light is split into the rainbow. This creates the range of colours of the rainbow called the spectrum of light. There are other parts of the spectrum that are not usually visible to the human eye. Infra-red is at the higher end of the spectrum and the ultra-violet is at the lower end. These light rays have a high energy and are the main cause of sunburn. When a substance gives off light under ultraviolet light it is said to be fluorescent. Many soap powders contain special dyes whci give a fluorescent effect to make your clothes look whiter (it does not mean that they are any cleaner!!).

Only some inks will shine in UV light. Other links, which appear to be the same colour, may show up as different colours.