Is all black ink the same? Black ink may actually be made of a combination of many different dyes.
Students will be able to determine what pigments are present in black markers.
- White coffee filters or paper towel cut into 1 inch strips
- 3-5 different types of black markers or felt tip pens (i.e. Expo, Sharpie, Pentel, Paper Mate)
- Cup with 1 inch of water
Pixels and Pigments Video
Teacher: Prior to the lesson, write a “ransom” note to students on a piece of paper towel or coffee filter, leaving ink on one end of the piece of paper towel and no writing on the other. This will be cut into strips later in the lesson. Assign each of the black inks to a character or person in the building who only uses that kind of ink. Tell students they are going to determine who wrote the note by investigating the ink.
- Cut the coffee filter or paper towel into strips about 1 inch wide.
- Draw a large dot 1 inch from the bottom of the strip of paper. Label the strips so you know which pen you used. Do the same for all ink being investigated.
- Hang the strip over the cup of water, touching only the very end of the paper towel and not the ink.
- Tape the coffee filter paper towel in place. The water will creep up the strips and separate each of the inks into a dye pattern called chromatography.
- Measure how far each ink sample travelled using the ruler. Make a line plot to record the data.
- Cut off a strip from the ransom note in the hook. The strip should have ink on one end and no ink on the other.
- Put the strip of paper towel in the water as you did before, allowing it to creep up and separate the ink.
- Take the strip out and compare it to the ink samples you took at the beginning of the lesson to determine what pen was used.