Magical color separation | Chromatography | English

Hello Friends, have you ever tired of mixing various colors while painting? You’ll notice that when you combine two or more colors, you get an entirely new color. Most of the sketch pens and markers that we use already have a combination of colors. Today we will learn how to separate these colors using a very simple method called chromatography.
Chromatography is a technique used for separation of individual components of a given mixture.
To learn this technique, we need three glasses, few sketch pens, filter papers, a plate, chalk pieces, wooden sticks, cello tape, and water.
Pour some water into the glasses up to about two centimeters from the bottom. Draw lines with red, black and blue sketch pen on filter paper strips at three centimeters from one of the ends as shown.
Tape a wooden stick on the other end of the filter paper strip. Suspend the filter paper strips vertically in the glass as shown. Make sure ink line remains about one centimeter above the water level. Notice the water rising in the filter paper.
Filter papers are made of cellulose. Due to the attraction between cellulose and water, the capillary action takes place, and water climbs up in the filter paper. The components of the ink dissolve in water and move with it. The sketch pen ink has either single or a mixture of multiple color pigments; each pigment has different solubility in water. The most soluble dyes move furthest on the filter paper while the least soluble pigment moves to the least distance, similarly the intermediate ones move according to their respective solubility thus separating the various pigments of the color on the filter paper. The separation of the ink molecules depends on differences in properties of dyes such as size, shape, mass, charge, and solubility.
In the filter paper marked with red sketch pen, you will observe red color pigment spread on the filter paper. Similarly, you see blue pigment when a blue sketch pen is used.
On the contrary, when you use a black sketch pen it gives a very interesting output. You will see multiple colors which are shades of blue, yellow and red pigments spread across the filter paper. The bluish color moves the farthest, whereas the red and yellow are found closer to the line.
Now that you have learned the science behind this let’s do something fun. You can draw various patterns using different color pens and filter papers.
Cut a circle with filter paper and make a hole at the center using a pair of scissors. Draw heart shape marks on this circle using brown sketch pens. Take a piece of tissue paper and make a tapering shape as shown and insert it into the filter paper. Place this assembly on the glass filled with water. Make sure another end of the tissue paper is immersed in the water.
Wait for few minutes you will observe separation of various pigments of brown color ink and finally, we will get a beautiful flower-like pattern on the filter paper. The pattern is made out of blue, yellow, green and red pigments. Observing these patterns against a bright light will show the shades of the pigments distinctly. Now go on and make your own patterns with the color pens you have at your home.
You can also try this experiment using chalk pieces. Draw rings on chalk pieces using color sketch pens. If you place the chalk piece in water, you will observe that the various pigments of the colors rise on the chalk piece.
We hope you learned some new today from these experiments.
To learn more such Fun hands-on science and math’s activities please visit our YouTube channel “IISER Pune science activity center”.
Have a fun!

Team: Ashok Rupner, Chaitanya Mungi, Shraddha Bhurkunde, Neha Apte, Sandeep Jadhav