Articles

    A STAMPede!

    Printing presses use rubber rollers to pick up ink and apply it to the surface of paper. Because of the chemicals that make up rubber, it has a way of picking up ink and then releasing the ink to paper. Rubber works because of the unique interactions between molecules in rubber and the molecules in ink and paper. So why can an eraser rub out pencil marks from paper? Because the attraction between rubber and graphite (pencil lead) is stronger than that between paper and graphite.

    Please note:  All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.

    Now let's make our own rubber stamps. Cut out a 5 cm square of cardboard. Draw a line down the middle of a rectangular pink school eraser. Now draw a simple shape (star or heart) on both the cardboard and on one-half of the eraser using a ball point pen. Fill in the shapes with a lot of ink to make them dark. Press the shapes down hard on a piece of white paper. Which one prints better? On the other half of the eraser draw a simple picture such as a flower or tree using red, blue and green ball point pens. See how many good clear prints you can make on your paper without re-inking the eraser.

    Use another eraser to make a stamp of your name. To have your name come our correctly when you print it, you have to write it backwards on the eraser. Add some designs around your name using different colors; be creative and have fun!

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    Kathleen Carrado Gregar, PhD, Argonne National Labs 
    [email protected]
    February 1994

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    Reference: "Wonderscience", 1993, 7(8), p.5.