Anyone who regularly uses a microwave oven already likely knows there are certain things which should never be placed inside one while it is turned on, such as silverware, batteries, and some plastics.
Some things are worse to microwave than other things, however, and this non-exhaustive list is an attempt to rate them from the mildest explosions to those which entail significant risk of personal injury or the destruction of the machine itself. For practical purposes, I will limit the list to food items, as the list of non-food objects which explode (with or without the help of a microwave) would be prohibitive in length for a writeup.
I will not describe how long or on what setting an item should be microwaved, in order to elicit an explosion, as that would be ethically irresponsible. This is more "how-not-to" than "how-to," but that writeup type isn't in the dropdown list.
Tier 1: Cosmetic Damage Items in this tier only "explode" insofar as their exteriors split open to allow steam to escape, making them less visually appealing to some, but otherwise having no meaningful effect on the quality of the food, or its threat level. You can still burn yourself on steam, but there won't be a "pop" or "boom."
Tier 2: Destructive
- Hot dogs and corn dogs - These will split down the side or turn themselves partly inside-out.
- Potatoes and sweet potatoes - The more dramatic version of what happens to hot dogs; potato explosion is easily avoided by cutting slits into the potato to vent steam.
- Eggplants (aubergines) - Potato logic applies: puncture it many times, and you're good to go.
Items in this tier will potentially damage the microwave and cause steam burns if handled carelessly.
Tier 3: Homemade Bomb
- Grapes - They literally emit plasma when microwaved, and they will explode into a scalding, sticky shower of said plasma, if jostled after microwaving them, if you stop the machine running before they explode on their own inside it.
- Oranges - Oranges behave like grapes, but bigger and with a thicker skin, allowing higher internal pressures to be reached before venting explosively.
- Carrots, green beans, and leafy vegetables - Raw carrots, green beans, and large quantities of leafy greens will all discharge electrical sparks when microwaved, due to trace metals absorbed from soil as they grow, and the center mass of a whole head of lettuce or cabbage can have significant steam pressure as well, which vents violently when handled.
Items in this tier will send you to the hospital or the morgue; permanent disfigurement is the best you can hope for if you actually bite into them right out of the microwave.
- Giant jawbreaker candies - These explode on post-microwave contact into razor-sharp shrapnel and boiling hot liquid sugar. They are easily the most lethal item listed here. The Mythbusters did an entire segment on the dangers of microwaved jawbreakers; I found it particularly impressive and recommend it to anyone who likes watching a room full of scientists be abjectly horrified.
- Raw eggs with an intact shell - These are only less dangerous than jawbreakers because they are smaller, and because eggshell makes less threatening shrapnel than hard candy shells do.
- Hard-boiled eggs, with or without their shell - The napalm-like burning gel makes liquid egg seem friendly and easy to get off skin, by comparison.
- Ceramic or glass mugs full of water - Water can get superheated in a microwave without beginning to boil visibly. When disturbed, such as by picking up the mug, the pre-boiling water can begin boiling out of the mug spontaneously, or explode outright, even destroying the mug. Ceramic shards moving at speed can tear up the microwave oven pretty easily. This issue also applies to breast milk, which is important for new parents to know, to avoid causing a horrifying accident when trying to prepare a bottle in a hurry.
- Tomato-based sauces such as pasta sauce - Steam pressure accumulates beneath the surface of the sauce as it heats, without being apparent to the observer. Many a mason jar and casserole dish has fallen prey to what one of my aunts dubbed "Ragù Napalm."
- Miniature pumpkins, gourds, squash, melons, and other fruit with a very dense exocarp - Depending how long you nuke it, you'll probably need to jostle it pretty hard to cause the detonation to be accomplished, due to how sturdy the exterior is, and I'm not sure why you would want to microwave an intact raw pumpkin or melon in the first place, since I can't think of any recipes that would call for it. Maybe you feel like destroying something beautiful. Maybe you just really want to fuck up the next person who opens that microwave door, or force them to buy a new machine. Regardless, there is a duration you can microwave a pumpkin, that will turn it into a very effective little grenade, without any further mechanical assistance.
If you insist on testing any of these for yourself, wear eye and ear protection, stand behind a sturdy wall or shield which protects all exposed parts of your body, have a fire extinguisher ready which is suitable for use on electrical appliances, and do not attempt it in any building you do not wish to see burn down.
Iron Noder 2020, 21/30