• Question: Why does an egg (with the shell) burst when cooked in a microwave oven?

    Asked by khughes08 to Hermine, Katy, Laura, Nathalie, Paula on 17 Jun 2010 in Categories: . This question was also asked by rebekah.
    • Photo: Nathalie Pettorelli

      Nathalie Pettorelli answered on 16 Jun 2010:

      Hi there,

      Eggs are a combination of yolk and white bits. When eggs are microwaved, different components in the egg expand at different rates (because the main constituents of yolk and white are different, one being mainly fat and the other containing a large proportion of water), which can result in the egg exploding 😉

    • Photo: Paula Salgado

      Paula Salgado answered on 16 Jun 2010:

      When you microwave any food, you are basically heating it. The temperature inside a microwaved egg can reach higher than 100C, so the water inside the egg becomes vapour. If the pressure from the water vapour is too strong, the shell can’t contain it and the egg explodes!

    • Photo: Laura Dixon

      Laura Dixon answered on 16 Jun 2010:

      The microwaves in an microwave oven are absorbed by the food being cooked. The waves heat water up and different parts of the egg have different amounts of water so heat up and expand at different rates. This expanding can be strong enough to break the egg shell and the egg explodes! 🙂

    • Photo: Katy Mee

      Katy Mee answered on 17 Jun 2010:

      Hi khughes08!! That was crazy chat session earlier – what year are you guys?

      I can’t say i’ve ever tried to microwave and egg and if i wasn’t on kitchen cleaning duties next week i’d give it a go when i get home from work tonight! It is to do with the fact that things contract (shrink) when they get hot so in the case of the egg, because microwaves heat up so quickly the egg just cracks – it’s the same if you drop an egg into boiling water, the shell will just crack. When volcanic lava is cooled really quickly, for example if it erupts on a volcano that is covered in ice, the same things happen, you get lots of tiny fractures. This is the kind of evidence i use in my work to try and figure out what the environment was like when a volcano erupted in the past

    • Photo: Hermine Schnetler

      Hermine Schnetler answered on 17 Jun 2010:

      Eggs (especially in the white bit) contain a lot of water. Water is very very absorbant when it comes to microwave waves. As the egg is in the microwave this water will heat up and begin vapurising, As this vapurisies the egg continues to harden and the pressure on the inside will reach a point that it exceeds the temperature acting on the outside of the egg, when this happens boom!!!! Egg splat.

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