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Author: Janice VanCleave


To measure the absorbency of a paper towel.


  • Scissors
  • l-inch (2.5-cm) -wide masking tape
  • 10-ounce (300-mL) plastic cup
  • Walnut-size piece of modeling clay
  • Pencil
  • Tap water
  • Marker
  • 4 identical 2-ply paper towels with as flat a texture as possible
  • Timer
  • Metric ruler



  1. Cut a piece of masking tape the same length as the height of the cup. Place this tape down the side of the cup.
  2. Divide the clay in half and use the two pieces to secure the pencil across the top of the cup.
  3. Fill the cup about half full with water and, using the marker, mark the water level on the tape. Label the mark 0.
  4. Take one of the paper towels, place the short sides together, and fold the paper towel in half three times in the same direction, producing a long, narrow, eight-ply strip.
  5. Fold the resulting strip in half, placing the short sides together. Crease the folded edge.
  6. Place the strip of paper towel over the pencil on the cup of water so that the fold rests on top of the pencil and the ends touch the bottom of the cup.
  7. Leave the paper towel in the water for 10 seconds, then raise it above the water and allow the water to drip from the paper towel for 10 seconds. Discard the wet paper towel.
  8. Mark a small line across the tape even with the new water level. Label this line l.
  9. Measure the distance from the zero mark to line 1 in millimeters. Record this number as the water absorbency number for test 1 in an Absorbency Data table like the one shown.
  10. Repeat steps 3 to 8 three times, using the remaining paper towels and refilling the cup with water to the zero mark for each test. Number the lines 2 to 4.
  11. Repeat step 9 for test lines 2 to 4.
  12. Average the absorbency numbers by adding the amounts absorbed in each of the four tests and dividing the sum by 4. Record the average in your data table.


The absorbency number of a brand of paper towels is determined


In this investigation, the term absorption is used to mean the soaking up of a liquid by a solid. The liquid is water, and the solid is the paper towel. Absorption by the paper towel is the result of the attraction between the water molecules and the attraction of the water molecules to the paper towel. The attraction between like molecules (water) is called cohesion, and the attraction between unlike molecules (water and paper towel) is called adhesion. In this investigation, there is cohesion between the water molecules and adhesion between the water molecules and the molecules in the paper towel. Because water molecules are more attracted to the paper towel than to each other, the water is absorbed, causing the paper towel to be wet.

The water moves through the paper towel because of capillarity. Capillarity is the tendency of liquids to rise or move through small tubes or openings of porous material, such as paper towels. The paper towel is made of tiny fibers that lie together, forming short, narrow spaces that act as tiny tubes. Water is attracted to the fibers, causing the water to move through the tubelike spaces in the paper towel. The greater the attraction between the water and the fibers, the greater the absorbency.

The absorbency number determined in this investigation is not a measurement of the volume of water absorbed. Instead, it is a number that can be used to compare the absorbency of different paper towels as long as the same measuring instrument is used.

For Further Investigation

Some paper towels are rougher in texture than others. Does a rough paper towel absorb more water than a smooth one? A project question might be, How does the texture of paper towels affect absorbency?

Clues for Your Investigation

  1. Repeat the experiment, using paper towels with different textures.
  2. Make sure the paper towels are the same size and the same ply. If necessary, cut the towels to a specific size, such as 10 inches (25 cm) square.
  3. If possible, use white paper towels without colored designs.


References and Project Books

Churchill, E. Richard. 365 Simple Science Experiments with Everyday Materials. New York: Black Dog & Leventhal,1997.

Hann, Judith. How Science Works. Pleasantville, N.Y.: Reader's Digest, 1991.

Nye, Bill. Bill Nye the Science Guy's Consider the Following. New York: Scholastic, 1995.

Reader's Digest. Why in the World? Pleasantville, N.Y.: Reader's Digest, 1994.

VanCleave, Janice. ]anice VanCleave's Chemistry for Every Kid. New York: Wiley, 1989.

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