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Shaping Hard-boiled Eggs

7 reviews


Active Time
30-45 minutes
Total Project Time
45 minutes to 1 hour
Key Concepts
Food Science, Chemistry, Protein, Coagulation
Sabine De Brabandere, PhD, Science Buddies
Mold Hard Boiled Eggs


Have you ever played with your food, creating funny faces or colorful edible artworks? In this activity, you can do just that, but with results you might not expect! You will learn a fascinating way to cook and shape boiled eggs, and explore some interesting chemistry about cooking an egg along the way. While exploring the flexibility of hard-boiled eggs, you will create a delicious, odd-shaped reward!
This activity is not recommended for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.


  • Plastic cubed box measuring 3.8 cm (1 1/2 inches) on each side. If you do not have one available, follow the directions in the Instructions section to make one using these materials:
    • Empty milk or juice carton, quarter gallon or larger
    • Craft knife or scissors
    • Tape
    • Ruler
    • Permanent marker
    • Pencil
  • Cooking oil or spray
  • Two extra-large eggs (less fresh eggs will peel more easily)
  • Saucepan
  • Water
  • Stove
  • Timer
  • Slotted spoon or spoon
  • Plate
  • Paper towels or kitchen towel
  • Oven mitt
  • Kitchen knife
  • Rubber band long enough to go around the square box

Prep Work

  1. This step explains how to make a cubed box measuring 3.8 cm (1 1/2 in) on each side from an empty juice or milk carton. You can move to the next step if you already have a cubed box this size available.
    • Wash the empty milk or juice carton thoroughly.
    • Cut it open so it lies flat.
    • Draw the template of an open folded box on the carton, with sides that are 3.8 cm. We have created the template for you to print, cut out, and trace on the carton.
    • Cut the template out.
    • Place a ruler along the fold lines and trace the fold lines with a pencil. This will create an indent in the carton and help create straight folds. Note: We advise you not to trace the lines on your mold as was done in the example pictures. The marker will come off on the egg, as you can see in the pictures, and also make it inedible. We only used the marker lines in the pictures to make the sections stand out more, to guide you.
    • Fold on the indicated lines to form a box, as directed in the template.
    • Secure the newly created box with tape, leaving one side open as a lid.

  2. Grease the inside of your square box with oil.


  1. Place two eggs in the saucepan. Add enough water so that there is a 1/2 inch of water covering the eggs. Put the saucepan on the stove.
  2. Heat the water until it comes to a rapid boil and keep the water boiling for 10 minutes.
  3. Turn off the heat.
  4. Use the slotted spoon to take one egg out of the water and carefully place it on a plate where it can cool completely. We will refer to this egg as Egg A.
  5. Use the slotted spoon to take the second egg out of the saucepan. We will call this egg Egg B. Do not discard the hot water; you will need it to keep Egg B warm.
  6. Place Egg B on several paper towels or a kitchen towel and carefully wrap the towel(s) around the egg. Use an oven mitt to protect your hand while you handle the hot egg.
  7. While still covered to keep it hot, gently tap the wrapped egg against the counter or a plate to crack the shell all over. Unwrap egg B and carefully peel away the shell. Place Egg B back on the spoon to dip it back into the hot water to wash away small pieces of shell. This also helps keep Egg B hot.
  8. Gently push hot Egg B, which now has all its shell removed, pointed end first, into the box without breaking the egg.
    Think about:
    How does Egg B feel? Is it wobbly, gel-like, rubbery or stiff? Is it possible to fit the hot egg in the box?

  9. The hot egg should just fill the box. If the egg does not completely fill up the box, add some folded paper towels on top of Egg B to fill the box completely.
  10. Gently close the lid on the box, squishing the hot egg in the box in the process. Put a rubber band around it to keep the box closed.

  11. Let both eggs—the unpeeled egg (Egg A) and the boxed egg (Egg B)—cool down for at least 30 minutes. Placing both eggs in the refrigerator can speed up the process.
  12. Once the eggs are cool, open the box and let Egg B slide out on the plate.
    Think about:
    How does the egg look? What is its shape? Touch it; does the egg feel differently than when it was hot.
  13. Carefully peel Egg A, the egg that is still in its shell, by gently tapping the egg on the plate to crack the shell all over and peel away the shell.
  14. Gently push Egg A, pointed end first, into the box.
    Think about:
    How does Egg A feel? Is it wobbly, gel-like, rubbery, or stiff? Is it possible to squeeze Egg A into the box without breaking it?
  15. After successfully molding an egg into a cube, cut the cubed egg (Egg B) open with a knife to make additional observations.
    Think about:
    What shape is the egg yolk of the cubed egg? Is it any different from the egg yolk in hard-boiled eggs you have seen before?
  16. Are you curious if a cubed egg tastes any different? This is your time to try it out!


If you have not already, you can eat your hard-boiled eggs or put them in the trash or a compost bin.

What Happened?

In this activity, you experienced how a hard-boiled egg feels like a wobbly, gel-like, flexible solid while hot. When it is flexible, you were able to squeeze it into the cube.

Both eggs cooled in their molds, one in a cubed box (Egg B) and one in the natural egg shell (Egg A).

Once cool, the eggs' shapes became permanent; one of your eggs was shaped permanently in a cube, the other in an egg shape. It was not possible to squeeze the cold, egg-shaped hard-boiled egg in the cubed box without breaking it. You could feel that the egg white felt stiff and rubbery.

A cardboard carton and hard-boiled egg both in the shape of a cube

After cutting the egg open, you saw the shape of the egg yolk changed as well. The egg yolk of the cubed egg was cubed and the egg yolk of the egg-shaped egg was spherical.

A cube shaped hard-boiled egg is cut in half and has a square yolk

All of this happens because proteins in the egg white unravel and create new bonds in the cooking process.

Digging Deeper

Egg white is mainly made up of water (about 85%) and protein molecules (about 10%). The proteins are twisted, folded and curled up like tiny, entangled balls of yarn floating around in the water. Heating causes the weak chemical bonds that keep these proteins entangled to break. The egg proteins then unravel and bump into other uncurled proteins, causing them to bond to one another, a process called coagulation. Water molecules are then trapped in a network of interconnected proteins and the egg white takes on a gel-like consistency, becoming a flexible solid. While the egg is still hot, the protein bonds are flexible and can be molded into different shapes.

Additional bonds between the proteins form until the egg is cold. The longer the egg is left at a high temperature, the more protein bonds form, and the rubberier the final egg will be.

Once the egg has cooled down completely, the egg white feels stiff. The protein bonds are permanently set, like a solid, and the shape of the egg can no longer be changed. The eggs can no longer be molded.

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For Further Exploration

  • In this activity, you molded eggs into a cube. You can mold eggs into other geometric forms. Here is a template to create a pyramid mold. Cookie cutters placed between two flat objects can lead to molds for even more shapes. What else can you create? Knowing a hot hard-boiled egg has a fixed volume, but not a fixed form, can you find the constraints of a mold's volume and form?
  • Try experimenting with the cooling time by creating an egg mold with your hands. Let cold water run briefly over the egg as you hold it to cool the egg abruptly. Does an egg instantly keep its form after abrupt cooling, or does it need long, slow cooling to make the form permanent?
  • In this activity, you mold hard-boiled eggs. Can you mold a soft-boiled egg? Can you find out how long you need to keep the egg at a high temperature for it to keep its form?

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