Smelly Eggs

Question: Why do eggs smell?

Rotten eggs are nature’s stink bombs – just one whiff is enough to send most people running! This egg-speriment shows you how to make your own guaranteed-gross “essence of egg.”


  • Small mixing bowl
  • Spoon
  • 1 egg
  • A 125 mL (1/2 cup) clear plastic disposable container with lid, or zip-lock sandwich bag or Petri dish (ask at your school to borrow one)
  • Adult helper


1. Break the egg into the bowl; then use the spoon to mix it well. Throw the
shell away in a compost or in the garbage.
2. Pour the egg mixture into the small container or zip-lock bag and seal tightly. (If using a Petri dish, fill with egg mixture until it is nearly full and place the lid on the dish.)
3. Set the sealed mixture in a sunny spot and leave it there for a day or two. You can do “smell checks” every now and then to see how your egg is progressing. Just lift the lid or open the bag and take a whiff (but DON’T TOUCH)! If the egg isn’t “done” yet, re-cover or reseal and let it sit awhile longer. Remember, there are no absolutes in this egg-speriment. The egg is “done” whenever you decide it’s done, but the longer you leave the egg in the sun, the more rancid your results will be.


An unbroken egg left in the sun for a few days can achieve the same reeking results. Just make sure that when you break the sun-ripened egg, you do it somewhere far, far away from anywhere your nose (or anyone else’s nose) usually goes, because it’s going to smell really bad.

What Happened – and Why?

Eggs contain sulfides – smelly compounds that are a mixture of sulfur, metals, and other organic elements. The sulfides don’t smell bad when the egg is fresh, but when the egg rots, the sulfides are released as stinky gases. (Here’s a big impressive word for you: the rotting process of organic matter is also called putrefaction.)

Source: Adapted from “Stinky Smelly Hold your Nose Science – A Real Bad Egg experiment. ” Kristine Petterson. 1997