The Science of Peeling a Hardboiled Egg

All twenty-four sets of eyes were watching me closely as I lit the match. After lighting the paper on fire, I placed it in the bottle and put a hardboiled egg on the opening. As the paper burned and smoked, the egg, slowly at first then more quickly, squeezed itself into the bottle as if some invisible hand was pushing on it. The fire went out and then the egg finished passing through the narrow opening and slid inside the bottle with a small popping sound. A few of the sixth graders clapped. Then I turned the bottle upside down so the egg was positioned over the opening again and gave a quick puff of air past the egg and into the bottle. This time the egg slid back out of the bottle, again, as if an invisible hand was pushing it again. This time, everyone clapped.

The invisible hand was air pressure of course and my demonstration, along with a lab I had set up for the students, allowed them to see how changes in air pressure do work as well as drive weather systems. My students always loved my demonstrations and the hands-on labs I had them do. It was all part of my effort to pay it forward. As part of the Sputnik generation, I was taught how to do science instead of memorizing science. And that has made all of the difference in my life. Exhibit A is peeling hardboiled eggs.

One of the hardest parts of the egg demo is getting properly peeled eggs. The shells of hardboiled eggs are notoriously stubborn about releasing their deliciousness cleanly. Peeled eggs often resemble a lunar surface. Within the last year, I had to exchange my morning breakfast bar for a hardboiled egg. At first, I simply bought eggs that were already boiled and peeled from the store. But they were overcooked, expensive, and had a short shelf life. So I embarked on figuring out if there was a way to peel eggs easily. After much experimentation, I found there was.

First, I did some research. The internet and YouTube all had guaranteed ways of peeling eggs. I collected the common ones and tried them all and most had some measure of success, but one method had more consistent results and with a little modification, has worked perfectly every week since I discovered it. Some of the methods I tried were useless such as adding baking soda to the water. Others, like shaking the cooked eggs inside a jar with water, worked partially but often destroyed the whole egg. Others worked some weeks but not others.

To keep things as consistent as possible, I bought my eggs (grade A large) from the same Walmart every Sunday afternoon and boiled six of them every Sunday evening in the same pot and on the same burner. I used a timer to cook and cool the eggs so my times were consistent. Many of the methods I studied said that older eggs were better than fresh. I can’t confirm that, but if I have the science right, freshness shouldn’t be much of an issue unless you raise your own chickens. Then maybe there could be a problem.

The key to peeling a boiled egg is to get separation from the inner and outer membranes of the egg. The shell is attached to the outer membrane so being able to lift that membrane away from the egg allows for the cleanest peeling. The method that I found that worked best was putting cold eggs from the refrigerator directly into boiling water. I should mention that I live at 8500 feet above sea level and the temperature of boiling water at my house is 91° to 92° Celsius. At sea level, of course, it would be 100°. This temperature difference could cause variations in cooking times at other altitudes. I put the eggs into the water using a slotted spoon to prevent breakage, and set the timer for twelve minutes.

When the timer goes off, I empty out the hot water, run some cold water over the eggs. Then I fill the pan with ice and ice water. Then I let it sit for 10-15 minutes. At that point, I start peeling the eggs under warm running water. It is crucial that I crack the fat end of the egg first on the counter. There is an air pocket on the fat end so it is easier to start to separate the inner and outer membranes by beginning there. I have also found that rolling the egg around on the counter while applying pressure breaks the shell into small easy-to-peel pieces. But it isn’t necessary. After two months of using this method I haven’t had a single egg that didn’t peel smoothly and quickly. And the yolks are just barely cooked which is the way I like them.

The science here is, I think, simple. Heat makes things expand by speeding up molecular motion and cold makes things contract by slowing motion down. Rapid, extreme temperature changes cause the molecules that make up the membranes to expand and contract at different rates making membrane separation easier. This method takes the egg from cold to hot to cold to warm very quickly. Every method I studied claimed to be the best way including the one that did, in fact, work. But in science, we don’t take somebody’s word for something if we can try it ourselves. And thus my report on the best way to peel a hardboiled egg.

We have a lot of problems in this country that require the services of scientists and engineers to solve. But science and math education in this country is pathetic and the attempts by the government to improve things by adding more testing just makes matters worse. Nobody in positions of power pays any attention to the recommendations of science and math education experts (who support specific hands-on instruction.) Instead, they listen to voters, parents, lobbyists, and Evangelicals. A significant portion of this country’s children are told twice a week in Sunday school that science (in the cases of evolution, geology, cosmology, and climate change) is not only wrong but will lead them straight to Hell.

And if that weren’t bad enough, there are even religious attacks on modern math concepts such as set theory. Combine that with the fact that many elementary math teachers do not understand math theory, and most secondary teachers are too good at math to help students who don’t understand, and we get a situation like we have now. Thousands of jobs go unfilled or to foreigners because there aren’t enough American STEM students to fill them. And everyone from the president on down pontificates but does nothing useful.

It’s so depressing that I think I’ll just go make a sandwich to console myself. Egg salad I think. Yum.