Demonstrate the ease with which invisible ink can be made with a few simple materials found at home. Gather milk, a piece of white paper, a small paintbrush or a cotton ball. Using the cotton ball or the paintbrush, write a message on the white paper. With the help of an adult, turn on the kitchen stovetop burners and place oven mitts on hands. Hold the paper roughly 12 inches above the burner. The milk will turn brown and reveal the message when heated.
Demonstrate how a forensic scientist identifies ink used in a criminal act by using chromatography. Chromatography is the process of separating a mixture into individual elements for comparison. Buy three brands of black felt pens, designating one as the culprit's pen. Fill a tall glass with water, and then cut out three strips of paper towel and attach them on to a paper clip. On each strip of paper towel, use different markers and draw one small dot. Place the strips into the glass, with the ink dots above the water level, balancing the paper clip on the rim. As the water soaks into the paper and the ink begins to separate, record results and compare with the culprit's pen to find the match.
Researching online or in the library, prepare a project about different non-invasive approaches for analyzing ink, such as micro-spectrophotometry and Raman spectroscopy. Both use ultraviolet light or infrared light for finding a distinct pattern in ink and also find similarities in chemical make-up of the ink used. Either one of these processes helps keep the condition of the documents being tested intact, lessening the risk of destruction. Explain why these approaches are used when working with older or more fragile documents, such as ancient manuscripts, instead of the more invasive chromatography process.
Gather fingerprints related to a crime scene. Have a volunteer hold a glass and record her fingerprint by dusting the glass with a small amount of cocoa powder. Lift the print with clear tape and secure on a piece of paper. Using an ink pad, collect several samples of fingerprints from suspects, including the original fingerprint from the actual "criminal." Place the single print on a piece of paper with the other volunteer prints for comparison, allowing the audience a chance to catch a thief.