While it may be possible to briefly – 15 to 20 seconds at most – reheat a hard-boiled egg without its shell, it is safest to avoid microwaving eggs. Reheating hard-boiled eggs with their shells still on in the microwave can result in scalding egg whites and yolk flying across the room. For your own safety and to keep your hard-boiled egg in one piece, try warming it with alternative methods. Using a bowl and boiling or hot water, you can allow a hard-boiled egg to come to temperature in not much more time than heating it in the microwave.
Can You Microwave Hard-Boiled Eggs?
No – the idea to microwave eggs in their shells is not a good one. When hard-boiled eggs are microwaved, even for as little as 35 to 40 seconds, the egg heats up, but is under so much pressure thanks to the shell that it explodes when it is touched. The yolks themselves can even reach the temperature of boiling water, around 215 F, when microwaved. That is not something that should come in contact with your skin.
Eggs explode in the microwave due to the pockets of water droplets that form inside them. As the yolk heats up, the tiny pockets of water also heat up, causing the interior of the egg to expand under the pressure that the shell exerts on the egg's interior. The pressure is also what keeps these water droplets from boiling. This is why the egg explodes when it is touched and the pressure of the shell is shattered.
How to Reheat a Hard-Boiled Egg
The best way to reheat a hard-boiled egg, or several, is to collect them and place them securely at the bottom of a medium or large mixing bowl. Use a kettle or coffee maker without coffee grounds to heat water. Once the water is boiling, pour it over the eggs until they are completely submerged and allow them to come to temperature.
If the egg yolk is runnier than you would like, let the hard-boiled eggs sit in the hot water for about two minutes to let the yolk cook a bit more. If you just want to reheat the egg, let it sit in the hot water for about one minute. Use a spoon to retrieve the eggs from the water and place them on a paper towel to dry.
Is the Egg Still Good?
Before you make hard-boiled eggs, try using the water test to see if the eggs are still good. To do this, gather your eggs and a medium mixing bowl filled with room temperature water. Place the eggs in the water one at a time. If they float, the egg has gone bad. If the egg sinks to the bottom and rests on its side, it is still fresh. Eggs that stand on one end or the other are still fresh enough to eat, but need to be used without delay.
Hard-boiling eggs is a great way to use eggs that need to be cooked because they can be easily stored. No need to eat all the hard-boiled eggs at one time. Once cooked, hard-boiled eggs will keep in the fridge for up to one week. Don't forget that hard-boiled eggs can easily be turned into deviled eggs, too.