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How strong are eggshells? The answer might surprise you. We often use eggshells as an example of something fragile - “walking on eggshells” - but is it really so? Or under what conditions might it not be so? This experiment answers that question.

• 4 Eggs
• Plastic Tape
• Sharp scissors
• Phone books

1. First, carefully break off the small end of the eggs and pour out the contents into the garbage.
2. Now, wrap tape around the equator of the eggs and gently cut a line through the center of the tape so that you get four dome-shaped shells. Discard the rest.
3. Lay the four domes on a table in the pattern of a rectangle with the cut sides facing down.
4. Get out the phone books, and see how many heavy books you can rest on the eggshells without breaking them!

How It Works:

The crowns of the eggshells form arches. Arches are strong because they exert horizontal and vertical forces that can resist a lot of pressure. The eggshells can resist the pressure of the phonebooks because the weight is distributed evenly throughout the shell’s structure.