Black dots
To our eyes, black looks like a single colour. But when you examine it, you’ll uncover that black ink is actually made up of lots of different colours.
Get started
Step 1
From a paper coffee filter, cut strips 1.5 cm wide.
Step 2
Take your strip and put a dot 1 cm from the bottom with the black felt-tip pen. Let it dry, then do it again in the same spot. Repeat this ten times, letting it dry a little each time. You’re adding more layers of ink each time.
Step 3
Stick a skewer through the top of the strip. Pour a little water into a glass – just enough so the bottom of the strip dips into the water. Make sure the water doesn’t touch the ink dot! Can you see what is happening?
Step 4
Did the water climb all the way up to the skewer? If it did, take the strip out of the glass and stand it in an empty glass to dry.
Step 5
Now try it again using black felt-tip pens from different brands.
What did you discover?
As the water climbs up the paper, it pulls the black ink with it. The ink separates into its different colour components as it travels, creating a faded, colourful spot. Some colours in the ink dissolve faster in water, so they travel further up the paper. Different brands of black pens use different colour mixes to make black.
Tip: don’t use waterproof pens – they won’t work for this experiment because their ink doesn’t dissolve in water.
