The Microwave Oven

It is an appliance that is in almost every home and restaurant in America, but do you know where it came from, or what it’s made of? I have come here to tell you exactly these things and more.

A common microwave you can find in over 90% of all homes in the US (Michael Hession)

I. Introduction

The Microwave Oven

Microwaves. There’s one in every home kitchen, office, and teacher’s breakroom. If you need to thaw out some meat for dinner, heat up the leftovers, or make a frozen meal, they’ve got you covered. But where did they come from? The first functional microwave oven came about in 1946, and it has gone from a large, expensive machine using magnetron tubes that had to be water-cooled to the easy-to-use appliance we see today.

Common Perceptions

I think this product is perceived by most people as one of the most useful appliances in their home. The convenience the microwave brings to the kitchen is unmatched by other cooking methods. My conception of this product pre-investigation is that it is a product that has been perfected over time, and is still evolving with different cooking modes and what-not, but probably took some time to get there. I believe others agree with me in that it leaves nothing to be desired in its function, but I doubt many (including myself until now) have wondered about its history.

Burning Questions

  1. How does it work? How do microwaves actually cook food?
  2. How did technology used for war end up in the kitchen?
  3. What are the innovations the microwave oven went through to get to this point?

II. Origins

Material Ingredients

Stainless steel: The most used material in a microwave is stainless steel, since it makes up the whole outside cover and door of the microwave. This steel is also used in many of the electronic components of the microwave, such as the magnetron. Stainless steel can be recovered from acquiring materials that come out of the earth such as iron ore, chromium, silicon, and nickel (Feng 2019). The process for making this material is to smelt the original compound or ore and casting it into the specific shape, then being cleaned and polished.

Common look inside of a steel smelting factory (Britannica)

Glass: The second most used material in a microwave is glass, which is used for the cooking plate and sometimes the window through which you can watch your food cook. This material is extremely heat resistant, which makes it great for the repeated use of a microwave. Glass is made by heating sand to extremely high temperatures and “blowing” it into the desired shape.

Plastics: The least used material in a microwave is plastic, most commonly of the polypropylene variety due to its cost-effectiveness and its combination of physical and chemical properties that aren’t as apparent in other varieties (E&T Fasteners 2021). This makes up the cables and washers in the unseen hardware of the microwave. Plastics are made from organic materials such as cellulose, coal, natural gas, salt, and crude oil (Feng 2019). Plastic is produced by refining crude oil and taking a fraction of the oil called naphtha and treating it with heat until it breaks apart into different polymers, which are then shaped into plastic.

Timeline

Discovery of Glass (Sometime in BCE): It is not known exactly when glass was discovered, but there is evidence of volcanic glass being used in the Stone Age and evidence of the first manufactured glass in the era of Mesopotamia. Without glass, it would be difficult to find another material with the heat resistance required for the microwave plate.

Invention of Plastics (1856): Parkesine is considered to be the worlds first manufactured plastic, patented by Alexander Parkes in England. It was made from cellulose treated with nitric acid, and paved the way for the modern oil plastics of today. Without plastics, the tubes and washers used inside microwaves would have to be made of an entirely different material.

Invention of the Magnetron (1910): The first magnetron was invented by Hans Gerdien in 1910, which led to the cavity magnetron tube invented by John Randall and Harry Boot in 1940. This device is an integral part of the microwave oven, because it is used to generate the microwaves used to cook the food.

A deconstructed look at a magnetron not unlike those used in microwaves today (Wikipedia)

Invention of Stainless Steel (1913): Harry Brearley of the UK discovered stainless steel when he was trying to solve the problem of eroding gun barrels during World War I. He added chromium to iron to produce a metal that didn’t rust. This is an integral material in the microwave, and its performance would not be possible without stainless steel.

Discovery of Microwaves (1945): The cooking power of microwaves was accidentally discovered by Percy Spencer in the US, when he noticed that a radar set he was analyzing had melted a bar of chocolate that was in his pocket. He then tested it on popcorn and an egg, which confirmed his observation. The cooking power of microwaves would simply not be possible without this discovery.

The First Microwave (1947): Soon after Spencer’s discovery, Raytheon rushed to build a commercial microwave oven. It was dubbed the Radarange, and was almost 2 meters tall and required water cooling. It sold for a whopping $5000, which is about $64000 today (Davis 2016). This device paved the way for the common microwaves we see today.

The first commercial Radarange from Raytheon in the 1940s. (Getty Images)

The First Turntable Microwave (1964): Between 1964 and 1966, Sharp Corporation from Japan introduced the first microwave with a turntable, which provided more even heating of the food. This is now the standard of microwaves you see in households today.

Additional Microwave Features (1974–1975): In 1974, Amana introduced the defrost function on their microwave ovens, and in 1975 they added a full digital display. This further innovated the microwave oven and brought us closer to the common ovens you see today.

Popularity and Affordability (1997): While not being an actual event, the year 1997 was a huge milestone for microwave ovens in the US, as the numbers showed that over 90% of households owned one, with average prices dropping down from the staggering $5000 for the Radarange to about $200 a unit (Davis 2016).

Microwave Steel (2004): In 2004, Jiann-Yang Hwang achieved “microwavable” steel by connecting six magnetrons from normal microwave ovens to make a giant oven and linked them to an electric arc furnace. When iron and coal were put into the oven, it first smelting the iron and then converted it into steel in a fraction of the time as normal steel smelting. Hwang has said that this could cut production costs in half!

III. Context

The lifetime of the average microwave oven used by a family is about seven years. That means every seven years the materials involved in the microwave are consumed by the customer, even if they keep the same oven that long. This raises an issue already, as there is a global developing shortage in high purity sand, the essential material used to produce glass. In addition to the sand shortage, there is obvious proof that ore concentrations in mines are getting smaller and smaller, which will greatly reduce our ability to find high-quality metals such as iron for stainless steel.

Research has shown that in the EU alone, microwaves consume 9.4 terawatt-hours of electricity per year, which takes several gas power plants to generate (Gallego-Schmid 2017). From their production, use during their lifetime, and disposal, this releases more than 7 million tons of carbon monoxide per year, an obvious problem for the environment. Consumers in the future need to be more aware of how they operate these products, such as cooking for appropriate times, so these numbers do not rise. Aside from the production of the microwave, the production of the stainless steel which makes up most of the microwave's material composition creates many times the emissions mentioned above (about 1.9 million tons per ton of steel produced).

While microwaves obviously contribute to emissions, they are overall the best cooking appliance to use from an environmental perspective. From the start, they created an alternative to natural gas run ovens and stoves, which has helped to slow down our consumption of this non-renewable resource over time. Even now, they require much less energy to run than new electrical ovens, therefore creating less indoor air pollution. They also produce less heat than other cooking methods which saves energy used in air conditioning. One technological trend microwave ovens are following is the introduction of “smart” technology. New microwaves being produced can be connected to the user’s smartphone or execute verbal commands. Another trend that is emerging is multi-function microwaves. They have always had the obvious conventional cooking and defrost options, but companies like KitchenAid are developing ovens that can air fry, grill, or use conventional oven techniques. This could actually be a good thing for the environmental impact, using fewer appliances and sources of electricity for different ways of cooking food, while still maintaining the efficiency of the microwave.

Energy efficiency of a microwave compared to other cooking appliances (Quora)

IV. Case Studies

New Microwave Settings (Cuisinart)

While this isn’t necessarily combating a problem with the microwave, this could help to limit use of other kitchen appliances that use more power and create worse emissions. If microwave oven technology could get to the point where you could grill and fry your food and achieve comparable effects as traditional appliances, then those other appliances could be phased out in the long run. The need for fewer appliances in the kitchen combined with the reduced energy usage would surely result in far fewer emissions being released into the atmosphere. Cuisinart has probably come the farthest in these innovations, with the newest edition of their microwave having eight cooking options including baking, roasting, and grilling.

Cuisinart microwave oven with all 8 cooking options
Result of roasting chicken in a microwave

Wayv Microwave Boilers

In the UK, the heat tech brand Wayv has developed a new type of boiler (water heater) using the same type of technology in microwave ovens. This innovation stems from the UK passing legislation that will soon ban new gas boilers from being produced, and this is a promising alternative. Instead of gas, these boilers obviously use microwaves, which could severely cut down emissions for the average household. These boilers are entirely compatible with existing plumbing systems as well, so these would be a quick and easy switch for most households.

The Wayv microwave boiler
Relative size of the boiler in a household

V. Action

An activity a reader could complete in order to see the microwave oven as an improvement in energy consumption in the kitchen over other products is to take leftovers of a dish that could be put in the microwave or the conventional oven, like let’s say leftover pizza. From the time to heat up to the actual time to reheat the food, the oven works for many times longer than the microwave for the same or similar result. Combine that with the fact that the oven consumes more energy per unit time, and the reader can clearly see that the microwave is the most energy efficient option. In this case, the time it takes to cook is much more effectively conveyed through an activity, because reading the words “a minute” and imagining it is one thing, but actually sitting through that minute and realizing how long it is is another thing all together. I also found a great tool you can try on your own as an estimate energy calculator to compare microwave and conventional ovens among other appliances at energyusecalculator.com. Just as an example, using a microwave for 30 minutes a day would result in 0.6 kilowatt-hours per day and a yearly cost of $21.90, while using an oven for the same amount of time results in double of both numbers.

VI. Analysis

After concluding my investigation about the microwave oven, I have found that this product is much more complicated than I initially realized. From the initial invention of the magnetron, its main component, and how microwave technology has sparked innovations in other areas in technology, such as the Wayv hot water heaters or the students at Michigan working to innovate steel production, this product has a much wider reach on society than strictly staying in the kitchen. As far as whether the microwave oven is appropriate or not, I would say it is very much in the middle ground. On the one hand, if used correctly, it is by far the most energy efficient cooking apparatus you can use in an everyday household. On the other hand, and this is not to say this does not apply to every other cooking appliance, but it is just another mass produced item that contributes to the increasing global shortages in ores, high purity sand, fossil fuels, and so on.

Honing in on the welfare aspect of appropriateness, I do not believe that the microwave excels in that region. Due to the complicated technology of the microwave, this type of product would be difficult to imitate in a more rural, underdeveloped area, where perhaps the access to electricity is limited or even nonexistent. For this type of setting, it would be more appropriate to adapt conventional oven technologies rather than microwave ovens, strictly because you can create an oven without using electricity. Talking about accessibility, you can make a case that there is plenty of accessibility now to mining materials, sand, and all the different manufacturing plants in order to arrive at the final product, but that accessibility is quickly dwindling. There will be a need some time in the future for material alternatives to come about, and they will have to apply to not only the microwave, but thousands of other products worldwide. Performance and value, on the other hand, are where this product shines. The microwave oven is unrivaled in the kitchen on the basis of energy usage, and in addition, it takes a fraction of the time to cook certain foods than through another method. Beyond that, the performance of microwaves is set to increase further and further in the coming years, with new developments in microwave technology where these ovens could be used to roast, bake, even air fry food, further distancing itself away from its other competing appliances.

My first question I wanted to answer by the end of my investigation was simply “how do microwaves actually cook food?” I did not have to dig deep for this answer, as it naturally presented itself during many portions of this project. The use of cavity magnetron tubes to generate the actual microwaves the oven uses was an extremely interesting topic to look into, especially learning about the real danger in the way it works, since if those waves escape the oven, it can cook many other things besides food. My second question was “how did technology used for war end up in the kitchen?” It was honestly pretty funny and surprising to me that the answer was not some elaborate, designed experiment to see if the technology would work. No, it was just a scientist who forgot to take a candy bar out of his pocket, and changed the world by doing it. My third question was about the innovations that the microwave went through to get to this point. I already touched on the magnetron being the first step, but the first microwave was a hulking 6 foot tall machine that used much more energy than it does today (and also leaked out radiation). From there, small improvements were made to decrease the cost and size and increase the effectiveness, and eventually it has gotten to where it is in the present.

I imagine at some point in the future the microwave will be the pinnultimate cooking appliance. It will be used to bake, grill, fry, toast, any and everything you could possibly want to do in the kitchen. I also envision a new shell for the microwave rather than the stainless steel one it is comprised of now, where hopefully there will be a practical replacement. All in all, I am excited for where this product in the future and I am glad that I not only have learned about its past, but also its possible future.

VII. References

Feng, Linyi. 2019. “Microwave Oven- Material.” Design Life-Cycle http://www.designlife-cycle.com/new-page-80

Gallego-Schmid, Alejandro et al. 2017. “Environmental assessment of microwaves and the effect of European energy efficiency and waste management legislation.” Science of the Total Environment DOI: 10.1016/j.scitotenv.2017.11.064

Davis, Amanda. 2016. “A History of the Microwave Oven.” IEEE Spectrum https://spectrum.ieee.org/the-institute/ieee-history/a-history-of-the-microwave-oven

E&T Fasteners. 2021. “Plastic Materials.” https://fastenercomponents.com/plastic-materials-ezp-12.html

EnergyUseCalculator. 2021. https://energyusecalculator.com/

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