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Activity: Making Algae Presses
NGSS Science and Engineering Practices
NGSS Crosscutting Concepts
Table of Contents


  • Several types of algae
  • Seawater
  • Containers for algae
  • Heavy paper (card stock, herbarium paper, or half of file folder)
  • Wax paper
  • Towels
  • Blotters such as newspaper, towels, fabric
  • Pair of cardboard backings cut to at least 8.5 x 11 inch
  • Weights such as books or bricks
  • Craft glue (optional)
  • Fan (optional)


  1. Choose an alga that you have identified and rinse any sediment off with seawater.
  2. Pat alga dry with a towel.
  3. Write your name and the genus or species name in pencil on the heavy paper so that the algae can be identified after pressing.
  4. Position the alga on your heavy paper so that it is centered. Spread out the thallus, branches, and blades. Be sure to position the alga so that any unique characteristics are visible. If the alga is a large thick clump, you may need to cut the alga in half so it will lay flat, or you may need to choose a smaller piece.
  5. Build your algae press (Fig. 2.38). If you are pressing a single alga follow steps a–f. If you are pressing several algae on several sheets, then repeat steps a-f as many times as needed.

    Fig 2.38. Diagram of algal press layers 

    1. Place a piece of cardboard down on the table.
    2. Put a blotter (newspaper, towel, fabric) on top of the cardboard. Blotters will help remove moisture from the alga in your press.
    3. Put your paper with algae positioned on it on top of the blotter.
    4. Carefully cover the algae with a sheet of wax paper.
    5. Add a second blotter to the top of the wax paper.
    6. Place a second piece of cardboard on top of the second blotter.
  6. Place heavy weights on top of your algae press so that the weight is evenly distributed on the cardboard above your alga.
  7. Dry algae presses. Drying may take up to a week for thick algae. Blowing a fan at the press will make the presses dry more quickly. Throughout the drying process, wet blotters may need to be swapped with dry blotters, especially if the alga is large.
  8. Once dried, carefully remove the wax paper from the alga, leaving the alga pressed to the paper. If needed, a small amount of glue can be used to secure the alga to the paper.
  9. (Optional) Identify and label any important features of the algae you pressed on the heavy paper.


Activity Questions
  1. Why is it important to preserve specimens?
  2. If you made several algae presses, was there an alga that was more difficult to manipulate and press? How would you change your pressing technique to address those difficulties?
Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.