Eggshells are often seen as fragile and delicate, but they are in fact incredibly strong and versatile. Let’s explore the science behind the eggshell’s surprising strength.
Eggshells are composed mainly of calcium carbonate, phosphorus and magnesium, and are only about half a millimetre thick. But an eggshell can withstand significant force when pressure is applied at the ends. This property makes eggs ideal for demonstrating the concept of force distribution in physics experiments. You can see a great demonstration here.
In this example, the experiment shows that you could in theory stand on an egg on its end, without the shell breaking.
The eggshell's shape is key to its strength: the shape supports the force along its long axis, which is the strongest part of the structure. This is also why eggs can be stacked on top of each other without breaking.
On the other hand, the same eggshell can easily be crushed when pressure is applied from the sides. The curved shape of the eggshell doesn’t distribute the force evenly in this case, causing it to break or crack easily.
Eggshells have lots of other unique properties that make them useful in a variety of applications.
Eggshells are a natural source of calcium, which can be used as a supplement in animal feed or in the production of fertiliser. In fact, because eggshells are 95% calcium carbonate, they’re an excellent source of this vital mineral.
Eggshells can also be used as a natural abrasive to clean surfaces, or as a substitute for chalk in art projects. Crushed eggshells can be added to soil to provide essential minerals and nutrients for plant growth, or around plants to deter snails and slugs. Birds love to eat eggshells, so scatter them outside around the birdbath or mix it into birdseed.
And here’s one for your disaster kit: eggshells can even be used to filter water in emergency situations, as their porous structure can trap impurities and bacteria.
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