Chromatography: Be a Color Detective
Do you love bright and vibrant colored art supplies? Do you ever wonder how these colors are made?
The variety of colors comes from colored molecules that are mixed into the material used to make the product. Some colored molecules are synthetic (or manmade), like the famous Yellow #5 found in food dyes. Others are extracted from natural sources, such as carotenoid (pronounced kuh-RAH-tuh-noid) molecules, which make your carrot look orange, and can be extracted from saffron.
Even though our eyes see a single color, is the color of a marker, for instance, the result of one color molecule or is a mix of color molecules responsible? This science project will help you in your quest to find the hidden colors in water-soluble markers.
This activity is not appropriate for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.
We see objects because they reflect light into our eyes. Some molecules only reflect specific colors; it is this reflected, colored light that reaches our eye and tells our brain that we are seeing a certain color.
Oftentimes, the colors that we see are a combination of the light reflected by a mixture of different-colored molecules. Even though our eye sees the result as one color, each of the separate color molecules stays true to its own color in the mixture. One way to see this is to find a way to separate out the individual color molecules from the mixture, to reveal their unique colors.
Paper chromatography is a method used by chemists to separate the constituents (or parts) of a mixture. The components of the mixture start out in one place on a strip of special paper. A solvent (such as water, oil or isopropyl alcohol) is allowed to run up the paper. As it does so, it takes part of the mixture with it. Different molecules run up the paper at different rates. As a result, components of the mixture separate and, in this case, become visible as strips of color on the chromatography paper. Will your marker ink show different colors as you test it on the filter paper
Extra: Most watercolor marker inks are colored with synthetic color molecules. Artists often like to work with natural dyes. It is fairly easy to make your own dye from colorful plants or spices like blueberries, red beets or turmeric. To make your own dye, finely chop the plant material, place it in a sauce pan and add just enough water to cover the plant material. Let the mixture simmer covered on the stove for approximately 10 to 15 minutes. If, at this point, the color of your liquid is too faint, you may want to remove the lid of the saucepan and continue boiling until some liquid has evaporated and a more concentrated color is obtained. Let it cool and strain when needed. Now you have natural dye. To investigate the color components of this dye, repeat the previous procedure, but replace the marker line with a drop of natural dye. A dropper will help create a nice drop. Let the drop of dye dry before running the paper strip. Would the color of your natural dye be the result of a mixture of color molecules or would it be the result of one specific color molecule? Does the marker of the same color as your natural dye run in a similar way as your natural dye?
Extra: In this activity, you use water-soluble markers in combination with water as a solvent. You can test permanent markers using isopropyl rubbing alcohol as a solvent. Do you think similar combinations of color molecules are used to color similar-colored permanent markers?
Extra: You can investigate other art supplies like paints, pastels or inks in a similar way. Be sure to always choose a solvent that dissolves the material that is being tested to run the chromatography test. Isopropyl rubbing alcohol, vegetable oil and salt water are some examples of solvents used to perform paper chromatography tests.
Observations and Results
Did you find that brown is made up of several types of color molecules, whereas yellow only showed a single yellow color band?
Marker companies combine a small subset of color molecules to make a wide range of colors, much like you can mix paints to make different colors. But nature provides an even wider range of color molecules and also mixes them in interesting ways. As an example, natural yellow color in turmeric is the result of several curcuminoid molecules, and the brown pigment umber (obtained from a dark brown clay) is caused by the combination of two color molecules: iron oxides (which have a rusty red-brown color) and manganese oxides (which add a darker black-brown color).
In this activity, you investigated the color components using coffee filters as chromatography paper. Your color bands might be quite wide and artistic, while scientific chromatography paper would yield narrow bands and more-exact results.
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Sabine De Brabandere, PhD, Science Buddies
Science Buddies |
Chromatography, inks, color molecules, primary colors
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