To separate the parts of ink.
- 10-ounce (300-mL) plastic cup
- 31/4-by-2%-inch (8.l-by-5.9-cm) basket-type coffee filter
- coin (quarter)
- green water-soluble marker
- 3-ounce (90-mL) paper cup
- tap water
- Set the plastic cup open side up on a table and stretch the filter over the mouth of the cup. Squeeze the filter around the sides of the cup to hold the filter in place.
- Place the coin in the center of the filter and, with the marker, draw a circle on the filter by tracing around the coin.
- Fill the paper cup with water.
- Dip your finger in the water, then touch the center of the circle with your wet fingertip. Watch the wet spot on the filter until no changes are seen.
- If there are any dry areas in the circle drawn on the filter, repeat step 6.
When water is added, the green ink begins to separate into different colors. Depending on the ink used, varying amounts of blue and yellow can be seen.
Ink is a mixture of a fast-drying liquid and pigments (substances that give a material color). The pigment in the dried ink on the paper dissolves in the water added to the paper. This watery mixture is absorbed by and moves through the paper. The different colored pigments have different amounts of attraction to the filter paper. The pigment with the least attraction will move a greater distance through the paper. Generally, blue pigment in ink moves farthest, followed by yellow. This method of separating parts of a mixture is called chromatography.
For Further Investigation
Mixing different pigments produces different colors. What pigments are in black ink? Do you think all black inks are made of the same pigments? A project question might be, How do the pigments in different brands of watersoluble black ink compare?
Clues for Your Investigation
- Repeat the investigation with different brands of black water-soluble ink. Write the name of each brand on the filter paper.
- Display the markers and the filter paper with your written conclusion of the results.
References and Project Books
Ardley, Neil. The Science Book of Color. New York: Gulliver Books, 1991.
Churchill, E. Richard. 365 Simple Science Experiments with Everyday Materials. New York: Black Dog & Leventhal,1997.
johnson, Mary. Chemistry Experiments. London: Usborne, 1981.
Lantier-Sampon, Patricia, ed. Smithsonian Institution: Color and Light. Milwaukee: Gareth Stevens, 1993.
Murphy, Pat, Ellen Klages, and Linda Shore. The Science Explorer. New York: Owl Books, 1996.
Potter, jean. Science in Seconds with Toys. New York: Wiley, 1998.
VanCleave, janice. janice VanCleave's Chemistry for Every Kid. New York: Wiley, 1989.
Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state’s handbook of Science Safety.