What color is your pen??

Remember...there is no color "black"?! As seen in a prism, white light refracts into all rainbow-colors, black not being one of them(, at least not during day-time). So how come they sell YOU black pens with "black" ink?? You can find the answer - if you wish to call it so - with the help of a very interesting, colorful and fun expercience you can do with your children:

What you will need:

1. Several coffee filters
2. Several different black pens (preferably felt, and not water-resitant)
3. Glass filled with water

What you should do:

1. Drink half of the water in the glass
2. Cut or rip a disk out of the coffee filter (diameter of disk > diameter of glass)
3. Draw a circle (diameter > 1cm) in the center of the disk and make a small hole in the middle of the circle
4. Make a small paper roll from another coffee filter and insert it into the hole from step three
5. Put the disk on top of the glass so that the paper roll touches the water
6. Wait 'n' c

Repeat for the other pens