Use a Microwave
Microwaves are electromagnetic waves with wavelengths ranging from as long as one meter down to as short as one millimeter, or equivalently, with frequencies between 300MHz (0.3 GHz) and 300 GHz. This is an extremely broad definition including: UHF (Ultra High Frequency--decimeter waves), SHF (Super High Frequency--centimeter waves), EHF (Extremely High Frequency--millimeter waves), and various sources use different boundaries.
Microwaves are great machines, and it can be daunting if you're new to them. Here's a guide on telling you how to work them.
Contents
Steps
- Read the instructions and safety warnings thoroughly. There's a lot of stuff you need to know in that little booklet.
- Plug your microwave in. Don't plug too many appliances in at once, or you may cause a power outage.
- Set the time that you want to microwave something for.
- If your microwave has a dial, turn it clockwise until the screen displays the desired time.
- If your microwave has a number pad, type in the desired number of minutes followed by the desired number of seconds.
- You may have to press "Cook" on your microwave before the time set will activate the microwave.
- Apply your understanding to microwave specific items.
- Start with Bake a Potato in the Microwave. If you are baking just one or two potatoes, or a sweet potato, reduce the power so the outside doesn't scorch by the time the inside is done.
- Warm a plate of leftovers at low power.
- Warm a milky coffee at medium power and check carefully when to stop so the milk retains its goodness.
- Make s'mores in a microwave for a graphic demonstration of a microwave's power of cooking food through all at once: the marshmallow rapidly becomes extremely large.
- Cook something big (but not huge, leave plenty of space on the sides, and stack loosely so some microwaves can enter into the core of the pile) at full power. For instance, a few pounds of potatoes to be mashed, piled all together plastic wrap or washed and returned to a plastic bag they came in, at full power. (Try fifteen minutes on high for five pounds.)
- Microwave chopped-to-size vegetables before frying them to get the inside somewhat soft without having to burn the outside.
- Make Microwave Popcorn, whether in a ready-made bag or in a covered bowl with a little oil (look around for a recipe). You might not expect from the rest of this article that it would work well, but it does. Follow the directions carefully; stop microwaving sooner rather than later -- it's better to have a mostly-full good bag rather than a full scorched bag. This generally should be done on full power to make steam to pop the little kernels rather than slowly fizzling the moisture out of them. Try elevating the bag off the microwave floor for more even cooking if you get a lot of uncooked kernels alongside some burnt popcorn.
Understanding Your Microwave
- Understand how a microwave oven heats food.
- Microwaves penetrate and generate heat at depth within water-bearing food. In contrast, almost all other cooking methods heat the surface only, whether by conduction as in cooking with a fluid such as hot air (roasting), steam (steaming), oil (frying), or water (boiling), or non-penetrating radiation as in broiling. (Convection is merely bulk flow facilitating conduction).
- Microwaves do not cook from the "inside out", but do cook thin food essentially all throughout at once, and reduce the depth within thick food to which conduction from the rest of the food must carry heat.
- Unlike boiling, etc. there is no hot dense fluid to carry heat to the interior of a large pile of food. Don't overstuff the microwave oven, even with somewhat loose items such as a big stack of potatoes.
- A microwave generally cannot cook food that does not contain much water, including something that is light and fluffy, well.
- Don't microwave something that contains little water for more than a minute or so before the microwave has a few minutes to rest, and put a cup of water in the microwave (which will get hot) with it to absorb the otherwise unused microwaves. This will help keep the microwave from overheating and damaging itself with surplus microwaves.
- Generally, don't expect something that is supposed to dry out in the cooking process, such as a cake, to turn out well unless you use a special microwave-adapted recipe.
- Microwaves tend to have many hot and cold spots from "standing waves". A turntable reduces this problem by moving the food through hot and cold spots. Very thin, flat solid food cannot conduct heat through itself rapidly to the cold spots. In some microwaves small or thin items cook better if they are supported above the floor by, for instance, an inverted bowl under a plate.
- Microwaves penetrate and generate heat at depth within water-bearing food. In contrast, almost all other cooking methods heat the surface only, whether by conduction as in cooking with a fluid such as hot air (roasting), steam (steaming), oil (frying), or water (boiling), or non-penetrating radiation as in broiling. (Convection is merely bulk flow facilitating conduction).
- Understand how heat flows through food. A cooking method heats only the outside of a food item--or in a microwave, the outer layers, perhaps an inch, enough to cook a two-inch-wide chunk more or less all at once. The heat must flow through the food to cook the rest.
- In a microwave, heat must also flow from better-heated to worse-heated spots.
- Water-based food--most food, and the only kind that microwaves can cook--cannot get hotter than 212 degrees Fahrenheit (100 degrees centigrade) until all of the water in the spot being heated has been boiled away. Applying more heat than sufficient to keep the outside from cooling below that point does not increase the rate at which heat flows into the interior to enable the cooking reactions (and to a very small extent, perhaps, be absorbed by them) by conduction through the watery bulk of the food. It only dries out the outside faster.
- You may be familiar with this principle through cooking a steak. One should use high heat only to scorch the surface, then low heat to cook the interior to the desired level of overall doneness without ruining the exterior.
- Pressure cookers keep water from boiling until it reaches a higher temperature, and, so, also cook extremely fast. But they are more or less limited to boiling (or, in the case of specialized commercial pressure-fryers for frying chicken, deep frying).
- Sometimes it is desirable to cook the food at an even lower heat, to allow the interior to reach the desired temperature and sit at it for a certain period without the outside having to get much warmer. This takes longer because there is a smaller temperature gradient to drive heat flow, but, even with the longer cooking time, can keep the reactions that would overcook the outside at near-boiling temperatures to a minimum.
- Consider sous vide. Try showing off with something "sous microwave", then seared, but start simple--perhaps by poaching an egg in plastic wrap--and be extra careful that anything involving raw meat or otherwise potentially hazardous is cooked through to a temperature sufficient to kill anything in it. Use a meat thermometer at several points. (There is little risk of something new bad developing in food during a microwaving process itself, because that is pretty fast.)
- It is very important not to overheat something containing milk, such as hot chocolate, even to boiling because the milk can irreparably separate.
- Watery foods, such as watery soups, can cook well at higher heat levels because they carry heat through themselves by convection. (Thick soups will not convect and will instead bubble locally and spit under excessive microwaving power.)
- Consequently, turn down the power if microwaving just a few items of food so the outside and hot spots are not overdone by the time the rest is done. Generally, use half power if heating something other than at least a large mugful of watery liquid or a heap of food a few inches high at least; even less--"defrost" setting or one-quarter power--for something already cooked and at risk of overcooking such as reheating chicken.
- If you have been scorching the outside of items before cooking the inside, just reduce the power at first--you don't necessarily have to increase the cooking time. Remember, the overly-high heat wasn't cooking the food faster, just drying it out.
- Understand the side-effects of other cooking methods, and choose to include them if you like.
- Some cooking methods, such as frying, smoking, or boiling with salt or spices, also add material and thus flavor to the food. Microwaving doesn't add anything, so add all the flavoring (including "liquid smoke", smoke particles collected in a very efficient manner and dissolved in liquid) you like to the food before or after cooking. Add conservatively: only a very small fraction of the medium in which something would otherwise be cooked is actually absorbed into the food.
- Some cooking methods add water to the food. Some, such as boiling (with water to be discarded) add way too much, so that it leaches out vitamins. Generally all that is needed with items prone to drying out is some plastic wrap with a few holes to prevent pressure buildup, but if something is on the edge of over drying, add just a little water and cover it.
- Some cooking methods dry out the outside of the food. Microwaving will liberate steam and re-moisten it, so if a crispy outside is desirable, generally microwave to get the inside mostly done, then cook the outside.
Tips
- If the food is covered during cooking, make sure to leave a small portion vented, or uncovered, so steam doesn't build up and burn you when the covering is removed.
- The foods should sit as directed in the recipe after being removed from the oven so the heat can continue to spread and dissipate. This is called 'standing time', but it is actually more cooking time.
- On the flip side, there can also be cold spots where the food doesn't get hot enough to kill bacteria. Follow stirring and rotating instructions carefully.
- Most ovens have hot spots, and if you eat the food directly from the oven, a few areas could be superheated and will burn.
Warnings
- Never operate a microwave if the door is damaged or doesn't close securely.
- Don't heat water or other liquids beyond the time recommended by the manufacturer or any recipe. Superheating can occur when plain water is heated in a clean cup for an excessive amount of time. The water will look innocuous, but when moved it can literally erupt out of the cup. Don't heat the water twice - that adds to the superheating risk. Adding sugar or coffee granules to the water will reduce the risk of superheating.
- Don't use metal containers unless the recipe specifically directs you to: as stated above, microwaves bounce off metal, which can cause arcing and a fire inside the oven. Some recipes may call for shielding parts of the food, especially meats, with small amounts of foil. This is perfectly acceptable as long as the directions are carefully followed.
- Don't operate the oven while it is empty. This can also cause arcing and start a fire.
- Make sure any glass, plastic containers, and plastic wrap you use are labeled microwave-safe.
- Plastic type 5 is the best type of plastic for microwaving, and most containers labeled microwave-safe are type 5. Plastic types 1 and 2 may also be safe if labeled as microwave-safe, but some caution against letting the container come in contact with food when heated.
