This is a transcript of the Gastropod episode Hotbox: The Oven from Turnspit Dogs to Microwaves, first released on June 5, 2018. It is provided as a courtesy and may contain errors.
LITTON AD: Microwave cooking units are indeed revolutionary. For a main course, how about a delicacy like lobster tails? Ready in less than a minute with no shrinkage or shriveling since there is no furnace-like blast of heat. This is cooking by microwave—cooking without heat.
CYNTHIA GRABER: I’m not sure I agree with this 1969 promotional video from the microwave company Litton. Revolutionary? I bet those lobster tails tasted like rubber, the part that wasn’t raw.
NICOLA TWILLEY: Hold your skepticism Cynthia, because this episode is all about humankind’s magical journey from that open fire to ever tinier boxes covered in buttons.
GRABER: We are talking about something a lot of you have asked us to cover: ovens! It may seem like your least fabulous appliance, but once we started looking into this topic—at your request—we realized we have a lot of questions.
TWILLEY: Just in case you started playing this podcast by accident, we are Gastropod, the podcast that looks at food through the lens of science and history. I’m Nicola Twilley.
GRABER: And I’m Cynthia Graber. And so, why didn’t microwaves revolutionize cooking as promised, and how in the world do they actually heat up my bowl of leftovers?
TWILLEY: Rewinding just a tiny bit, why did we first start using fire to cook our dinner—and what changed when we did?
GRABER: How did we get to the modern oven, where you don’t see fire at all? And finally, what about the billions of people in the world who still cook over wood fire cook stoves that are smoky and harmful to their health—why is it so hard to help them switch to something better?
TWILLEY: All this plus a few smoked sausages and exploding eggs.
RICHARD WRANGHAM: Oh, well I had a kind of absurd introduction to the problem because I was studying the feeding behavior of wild chimpanzees. And I tried to eat everything that chimpanzees ate and I even tried to go for days at a time eating only what they ate.
TWILLEY: This is Richard Wrangham. He’s a Harvard anthropologist, and in 1972, he was in Tanzania, studying chimp behavior. And it didn’t take him long to figure out that eating like a chimp was not much fun.
WRANGHAM: It left me incredibly hungry. Even though what chimps eat is not the same as what hunter-gatherers eat, it led me to the thinking that there’s something very different about living as a wild animal eating raw foods, and living as a human. And then, you know, I realized that every human eats their food cooked. So I started developing the idea that humans have something special about them. We need cooked food.
GRABER: Richard eventually wrote a book called Catching Fire: How Cooking Made Us Human. Fire and cooking—that’s what allowed us to get more calories from our food and spend far less time and energy to eat and digest it.
WRANGHAM: So if we were a chimpanzee of our body size, we would be expecting to eat something like six or seven hours a day. And in fact humans all over the world, regardless of what kind of subsistence society they live in, they eat for less than an hour a day.
TWILLEY: And with all that spare time, plus the extra calories, we humans could develop language and tools and culture and gigantic brains like mine.
GRABER: Just yours?
TWILLEY: Some days I think so. But maybe you too Cynthia.
GRABER: Thanks, appreciate it. So using fire to cook our food—that was revolutionary. It changed the course of human history—it changed the trajectory of life on earth. But cooking over an open fire was pretty much it for millennia. That was how we cooked.
TWILLEY: And now we mostly don’t. Sure, sometimes when we’re outdoors, but for most of us, dinner is no longer cooked over a fire. Cooking over a fire indoors?
BEE WILSON: It just looked and smelled so alien to anything that I’ve ever thought of as cooking.
TWILLEY: This is Bee Wilson, one of Gastropod’s most favorite guests—she was in our very first episode, and another on how we learn to eat, and we love her.
GRABER: But that’s not the only reason we called Bee up this episode. She’s also written extensively about what happened when we cooked over fire and the development of the oven in her book Consider the Fork. Which is absolutely awesome.
TWILLEY: And in that book, she describes the experience of watching a man called Ivan Day roast meat over an open fire.
WILSON: I mean, it was really the art of fire management. It was magnificent.
GRABER: Ivan is known for his work recreating historic forms of cooking and historic meals in Britain.
WILSON: Here was a man having huge fun poking a fire and producing roast meat that tasted better than any roast meat I had ever eaten before. Except as Ivan rightly pointed out, I never had eaten roast meat before, because what I had thought of as a roast dinner was really just meat baked in the oven. Whereas in Ivan’s kitchen, he was standing there before this blazing hot open fire. And I’d heard people talk about blazing hot fires before and I’d been in front of many fires that are lit almost for ornamental purposes in the winter but a cooking fire is just something else altogether.
TWILLEY: The fire itself was impressive, but the taste of the roasted meat—that was truly next level.
WILSON: It was soft and tender but had this wonderful, savory, umami beefy crust on the outside and it just made me feel that somehow all of the other meat that I’d had that had been roasted in an oven had sort of—it was as if the flesh had seized up by comparison, whereas this meat you could tell it had cooked very, very slowly.
TWILLEY: Yes, I’m drooling.
GRABER: I am getting hungry. Frankly, this is why people love barbecue. Because it’s delicious.
TWILLEY: And I promise, one day we are going to spend an entire episode on the curious history and science of barbecue, if only so I have an excuse to eat my body weight in delicious, delicious, smoky deliciousness.
GRABER: But the roasted meat that Bee was eating wasn’t just for fun or for a big cookout, it was how you cooked in 1600s England—and it’s not quite as romantic as it sounds. Imagine that huge, hot fire—it had to be really big to cook with—imagine that super hot, super smoky fire inside the house where you live.
WILSON: So one of the things to say is that in the days when people cooked over an open fire, most people didn’t have a kitchen. There was just one room where you cooked and lived and slept and that smokiness must have permeated everything.
GRABER: But an upside of the hearth being so central—it was sometimes the only warm spot in the house.
WILSON: The fire was the central focal point. And I hadn’t fully appreciated before I wrote my book that that Latin word focus means hearth. I mean the fire was the thing that everyone congregated around—it was what gave meaning to your life.
TWILLEY: That central focus is gone, and another thing that mostly went with it are all the special long-handled tools you need to cook over an open fire. But some things you still see today, like a spit, which is a stick or rod that you put through the meat.
GRABER: Sara Pennell is a historian at the University of Greenwich and she wrote a book called The Birth of the English Kitchen, 1600 to 1850. Sara pointed out that having that spit to roast meat on wasn’t enough—for most of history, you had to have a person to turn the spit.
SARA PENNELL: And depending on what sort of household you’re in that could be female person power or child person power or in elite kitchens it was often it what the most lowly boy employees were set to do.
TWILLEY: But there were also such things as turnspit dogs.
TWILLEY: This was a special kind of dog, with a long body and short little legs, bred to run on a wheel that turned the spit around so the meat got roasted through. This breed is now extinct—some people say its closest relative is a corgi. But Sara says they really weren’t super common in the first place. It’s not like every kitchen had its own turnspit dog.
PENNELL: It’s not that they didn’t exist but they were very sort of regionally specific.
GRABER: Whether or not the turnspit dogs were common, the roasts were not only common, but they were incredibly famous. This is what British food was and is famous for, roast meat. Roast beef.
TWILLEY: There was even a patriotic song about roast beef. I don’t know the tune, sadly, so you’re spared me singing, but here’s how the lyrics go: “When mighty Roast Beef was the Englishman’s food, It ennobled our brains and enriched our blood. Our soldiers were brave and our courtiers were good. Oh! the Roast Beef of old England!”
GRABER: I have never sung a song to roast beef, though Bee’s description sounded worthy of a ballad. In fact, I’ve never heard of any song devoted to meat at all. I’d also never realized that the fame of the British roast can be directly linked back to the nature of the British landscape.
WILSON: I found this really interesting, because I think so often when we talk about food we assume that somehow the taste comes first and that the English just happened to have a taste for roasted meat and we don’t think about the resources and technology that lie behind it. And we partly became a nation of people who ate so much roast beef because we were so well endowed with firewood. It was a really densely wooded green land, which meant that we could be really prodigal in the amount of logs that we threw on a fire and roast these great haunches of flesh.
TWILLEY: You can really see the difference that England’s plentiful forests made by comparing British cuisine to that other countries.
WILSON: If you look at other cultures like China where very early on they established the principles of wok cookery and stir frying, where meat was chopped very small and small amounts of it were used almost as a seasoning relative to the vegetables. And that’s conversely a cuisine of frugality and scarcity out of which great ingenuity was born. Whereas the English way of doing things, it’s a huge luxury to have that much fuel and that much meat.
GRABER: This meant the Brits got to rest on their well-wooded hills.
TWILLEY: Singing our beefy songs.
GRABER: Until they started to reach the end of their forest riches.
PENNELL: So coal becomes more widespread as a domestic fuel partly because of wood famine. You know, by the end of the 16th century, some areas are simply running out of wood as a fuel. And it has other purposes as well, obviously, for building ships and so on. It’s also to do with the opening up of coal fields in the northeast.
TWILLEY: Suddenly, fuel economy is the mantra of the era. This is in the second half of the 1700s. And not only is wood starting to become scarce and coal mining starting to be an industry—there’s also the fact that people are moving to cities. And when you live in a city, it’s often a very long walk to go and collect wood, but someone can bring coal to your door.
GRABER: And in your new urban house, you don’t have enough space to have a huge, open wood-fired hearth in any case. Luckily, with coal, you don’t need it.
PENNELL: When you start burning coal, you can have a smaller hearth because it’s a more intensely burning fuel.
TWILLEY: These new coal cooking fires weren’t just smaller. Very early on, people started enclosing them a little—they’d put a grate over top the hot coals.
PENNELL: And from that you start getting side hobs for putting pots and pans on. And that then becomes the possibility of, well, we still have this open flame in the coal grate in the center. But what happens if we put a metal box alongside that we could heat the water in? And then we get manufacturers thinking, well, we could also sort of somehow create an oven on the other side.
GRABER: So now with coal, we’ve gone from just a flame to something that directs that heat to a metal box—basically a proto oven.
TWILLEY: The enclosed oven was the hot tech breakthrough of the 1780s—Sara says the most frequently submitted patents that decade were for new domestic ovens that promised to be ever more efficient and safer and smaller.
PENNELL: The rising cost of fuel is making fuel economy a real focus for domestic reform. And probably the most famous person in this regard is in fact born in America: Count Rumford. Benjamin Thompson, Count Rumford.
GRABER: Benjamin Thompson, Count Rumford, was born in Woburn, not too far from me in Boston, but he fought for the Brits during the revolutionary war and then moved to London. He was a physicist. He moved to Munich and was eventually made a count of the Holy Roman Empire, in Bavaria.
PENNELL: You know, one of these fantastic polymathic characters. He’s a soldier but he’s an inventor.
TWILLEY: One of his early inventions was something that he saw as the solution to world hunger: Rumford Soup. In his opinion, this soup delivered the maximum nutrients for the minimum amount of money. Problem solved.
GRABER: As if.
TWILLEY: So then Count Rumford turned his attention to fuel economy.
PENNELL: So he invents a number of stoves and cooking ranges precisely to maximize the efficiency of fuel.
GRABER: Rumford’s main innovation was to create lots of small, enclosed coal fires in little brick ovens, so that instead of just one large cooking surface, you had lots of little tiny closed brick fireplaces, one per pot. Each had its own door and its own tiny chimney. Apparently it was genuinely more efficient.
PENNELL: These were installed mainly in institutional kitchens. So there’s a famous Rumford cooking stove in the Foundling Hospital in London. But he also had them sort of installed in supporters houses and then they were opened up for people to come visit and see in action.
TWILLEY: One of these Rumford stoves was in the house of a guy called John Sinclair, who at the time was President of the Board of Agriculture, and it was literally open 24/7 for people to come and see, in his house.
PENNELL: I love at the end of the 18th and the early 19th century there’s this exhibitionary zeal around people sort of seeing these new kitchen inventions in action.
GRABER: But despite that exhibitionary zeal, Rumford’s stoves didn’t really catch on. Coal-fired ovens were more efficient than wood ones, yes, but Bee writes that many coal-fired ovens still belched fumes from coal smoke.
TWILLEY: Not all of them had all the careful little chimneys that Rumford designed into his stove. In the newspapers at the time, these badly constructed enclosed coal stoves were called “poison machines.” They were known for filling the kitchen with noxious gases.
GRABER: Whether wood or coal, people in England were in general slow to switch from open hearths to ovens. They liked their flames.
TWILLEY: But wait a minute here. As fond as I am of roast beef, one cannot live by that alone. What about bread? What about baked goods? Were there really no enclosed ovens in England till the late 1700s?
GRABER: Well, in the Britain they did at one point have something called a beehive oven—this was actually invented by the Romans and they were popular for a while. They’re clay ovens, just like the clay tannurs that developed throughout the Middle East. So yeah, people in the Middle East had ovens, but in Britain, no, really, no real household ovens.
WILSON: You never would have had an oven equivalent to the ovens we have today. If you wanted to cook something like bread you would probably take it to the baker. That was a big thing, that people would take their dishes to a communal bread oven to be cooked.
TWILLEY: OK, so roast beef at home, baked dishes in the community oven. No wonder then that, at least in non-clay oven cultures like England, putting that hearth fire in a box was such a big leap forward.
GRABER: By the end of the 1700s, most British cooks had moved from wood to coal. But Bee says the next change in fuel was the real breakthrough.
WILSON: The real great leap forward was not coal but gas. It’s never really been given the credit that it’s due. That was one of the single greatest contributors to human happiness in the kitchen.
GRABER: That is quite a claim—gas as one of the single greatest contributors to human happiness in the kitchen?
WILSON: If you take a technology like gas that enabled people to do the things they did already, which is to get a delicious dinner on the table, but to do so at a fraction of the cost and a tiny fraction of the risk to personal health—that’s great. It’s magnificent. And that is what gas cookery did. It made life pleasanter, it made life more convenient. It meant that you could switch fire on and off at will, which is an incredible leap forward.
TWILLEY: All that smoke from wood or soot from coal—gone! And the work and dirt of lugging logs and lumps of coal into the house—also gone!
WILSON: And then all of the cleaning out of the fireplace. It was so dirty, it was so sooty. And gas at a stroke liberated people, specifically women, from all of that work.
GRABER: Gas was also far more efficient. But the biggest thing is that people were no longer chained to their hearth or their wood- or coal-fired oven.
WILSON: It’s amazing if you think how much people were just enslaved by looking after the fire, making sure that they weren’t burnt as they slept by the fire at night, I mean, you know, that was a really important job. We talk about curfews as being a time that teenagers have to come back. But actually the original meaning of that was it was a cover that people put over the fire at night to make sure that the house didn’t burn down.
GRABER: I had no idea that was what curfew originally meant.
TWILLEY: But for all its curfew-breaking allure, gas didn’t catch on right away.
WILSON: The amazing thing is that it took almost a century from the first experiments with gas cookery to gas becoming generally used in mainstream British kitchens, and then the rest of the world. But it was partly that gas as a technology, it had to be supplied by a gas company. And it’s one of those inventions a bit like an electric car where you think, there’s this whole infrastructure that has to be in place in order for people to be able to cook with gas stoves.
PENNELL: Unlike coal which gets delivered to your door or wood that you go and collect, you know you can’t go and collect gas—it’s got to be piped into your street and into your house in order for you to have the equipment that is run on it. So it’s an urban phenomenon in the main first.
GRABER: So, as you’ve been listening, maybe you’ve been wondering why we’re telling the story of the how open fires got turned into ovens in the UK and not in the rest of the world that did in fact use ovens for thousands of years. This is why—this series of really rapid, really significant transitions.
TWILLEY: On the one hand, England is late to the oven party—we didn’t come to the domestic oven till much later than say the Middle East—so we can see the change happen really quickly when the wood runs out.
GRABER: And then on top of that, the Brits innovated quickly because that moment in history, the lack of wood and the movement to ovens, it coincided with the industrial revolution and rapid urbanization.
TWILLEY: And the result is a century of frenzied oven innovation, where you can see people inventing and resisting and adapting to all these new cooking techniques in what is actually quite a short period of time.
GRABER: And speaking of resisting, even once the gas-delivering infrastructure was in place, people were still a little nervous about these life-changing ovens.
WILSON: You have to have somebody piping the gas into your home and people were very resistant at first. People were terrified of gas. They thought it was going to make the food taste and smell disgusting, they thought there would be explosions. Servants were said to be especially terrified that they were going to die by the gas.
TWILLEY: On the other side, there were gas boosters. Celebrity chefs endorsed cooking with gas, the gas companies promoted it, and there were public demonstrations, which were sometimes not completely successful.
WILSON: There were some account of some Victorian dinner that was done that was meant to publicize the wonderful benefits but everyone came away saying that food tasted a bit strange. But I mean it really probably, as with lots of things, took lots of other people to try it and survive and pass on the benefits.
GRABER: The gas stove users did in fact survive, and even thrive. But although gas was, as Bee said, probably the greatest leap forward in our kitchens, it wasn’t an unqualified blessing.
WILSON: So something is always lost as well as gained with these leaps forward.
TWILLEY: I mean, if you think about it, we are the cooking ape, as Richard Wrangham likes to say. We’re defined by our relationship with fire, and these new-fangled gas stoves are a huge shift in that relationship.
WILSON: It is also arguably the point at which fire stops becoming the focus of our lives.
TWILLEY: Sara says that this shift away from the open hearth was a topic of much debate at the time. People fretted that something important was being lost.
PENNELL: There’s a lot of discussion around the reform of the kitchen hearth, which is contesting the benefits of technology over the cultural values of tradition and the open hearth. You know, the open hearth in kitchen is culturally important.
GRABER: People missed the sense of that focal point in the home, the flame as the center of their houses. But they also missed the actual taste of the food cooked over that flame.
PENNELL: There is both a sort of sentimentality about it but also a sense in which actually, you know, food does taste better. And Acton is very clear on that—meat baked in an oven is dry and tasteless.
TWILLEY: Sara is talking about Eliza Acton, who is a food writer who wrote one of the first domestic cookbooks in England, at around the time of this transition. And in her firmly held view, gas ovens smelled unpleasant and were the quickest way to ruin your Sunday roast.
GRABER: And as I’ve been made well aware, a delicious Sunday roast beef was absolutely central to British identity.
TWILLEY: Which brings me to my secret theory about why British cookery has such a bad reputation. It all has to do with the demise of the real roast.
WILSON: I have that theory too. I really share that theory, that we had this one thing that we were completely brilliant at. I mean it’s—having seen Ivan Day doing it, it’s not easy. And then suddenly open fire cookery goes out and we lose the tools, we lose the knowledge, and we have nothing to take its place, so we somehow feel at a loss. We never had learnt to cook things, to stew things in a pan in the way that the French had done. You know, cookery writers in the 19th century would say: the British just have no art of soup making in the way that the French do. And it’s partly maybe we could be blasé because we could make ourselves these fantastic meals from roast meat.
TWILLEY: I’m just wiping a tear away here—see! My people were good cooks! We just used up all our wood and lost our mojo.
GRABER: Three hundred years ago.
GRABER: But change is inevitable. And it’s always hard. Sara says that each of these oven transformations—from open to closed and from wood to coal to gas—every change inspired complaints and reveries for the way the food tasted before. Take John Evelyn—he was a famous British writer in the 1600s.
PENNELL: And we can go back actually to the 1660s and John Evelyn is no less nostalgic about the change to coal. He laments the loss of those succulent sausages that you could smoke up your chimney. You can’t do that with a coal fire. Everything is sooty and charred.
TWILLEY: So much loss. And there’s more to come, at least in terms of de-skilling the domestic cook.
GRABER: Bee might think that the transition to gas is the single greatest thing to have happened in the kitchen, but it has some serious competition in the form of the super unsexy sounding thermoregulator.
ELIZABETH SILVA: It was in the early 1920s when this technology was developed in Britain, in Birmingham. And, you know, it depends on the calibrated dial with numerical degrees. And it would indicate the different temperatures that the oven could be set at.
GRABER: Elizabeth Silva is professor emeritus of sociology at the Open University in the UK. And this thermoregulator did what it sounds like—it regulated the temperature in the oven.
TWILLEY: Before it was invented—i.e. for most of human history—people had all sorts of ingenious ways of figuring out how hot their fire or oven was. We talked about this in our episode on the history of cookbooks—people would watch to see how quickly paper turned yellow in the fire or the specific color of the flame.
SILVA: There was this wonderful account of a woman born in 1902. And she was describing what she did need to know for cooking. She was saying that once she had a bed of coals she knew that it took four quarter logs to hot it up enough to bake bread. But if she wanted to cook muffins she needed to stoke up the fire and stuck her hand in and started counting. When she got to eight before it was too hot for her, she could cook the muffins.
GRABER: This was a highly sophisticated level of knowledge. People looked down on cooking, it was women’s work, but cooking took a lot of know-how.
TWILLEY: And the thermoregulator took some of that cleverness away from the cook, and put it in the oven.
SILVA: You no longer needed first to put your hand in and assess the heat of the oven with your body. You didn’t need to pay much attention. You just knew that for cooking a certain dish, you needed the oven at a certain temperature, and you would just set the dial to that and you could go on and do your gardening. You could do your sewing, you could do childcare or whatever. And it was freeing the time of the woman, who no longer needed to know very much about cooking.
GRABER: This innovation just so fortunately coincided with a time in which middle-class women were losing their servants. Cooks in the 1920s and 30s could make more money doing other jobs.
SILVA: So the middle-class women, they had to learn to cook and they needed the task to be made easier for them. So in many ways these kinds of cookers replace the servants.
TWILLEY: It’s another moment where a big shift in cooking technology is about innovation, sure, but it’s also about much broader changes that are happening in the world.
GRABER: Just a few decades later, the way the we heat food would be rocked by another technological innovation—one that also came along with some pretty major international events.
RAYTHEON TAPE: In America the main manufacturer of radar components during World War II was Massachusetts Raytheon Corporation.
TWILLEY: Raytheon actually manufactured about 80 percent of the magnetrons—the microwave-emitting devices that make radar work.
RAYTHEON TAPE: In early 1945, Raytheon engineer Percy Spencer was hard at work in the lab to improve these glorious machines. One afternoon, Spencer got hungry while he was working. He reached into his pocket for a chocolate bar and was flabbergasted to pull out a gooey mess.
TWILLEY: So what had happened to Percy LeBaron Spencer’s chocolate bar? Well, let’s back up. The magnetron was originally developed to spot Nazi warplanes.
GRABER: But now the war was over, and Raytheon wanted to find a way for this radar technology to be useful for something other than spotting Nazi war planes. They wanted to sell it to civilians. And Percy Spencer got an idea.
RAYTHEON TAPE: Spencer was inspired. He sent an assistant for a bag of uncooked popcorn. Then he spread the corn over the table near the magnetron and waited. Less than a minute later the kernels began exploding. Spencer was now certain that the microwaves themselves were doing the cooking and it was an auspicious beginning. Percy Spencer had made the first batch of what would become the world’s most popular microwaved food: popcorn.
TWILLEY: The next morning, Percy exploded an egg for a colleague. Clearly, this device was going to be a hit in the kitchen!
GRABER: Percy worked with his colleagues at Raytheon and turned that radar into an oven, the original microwave. But not the kind that you see at home. This one weighed more than 600 pounds and cost $3,000, which at the time was the equivalent of a year’s salary.
TWILLEY: It was called the Radarange—the winner in an employee competition to name this magical new oven.
GRABER: The Radarange was so powerful that the cooking times for recipes were in seconds—like a 50-second baked potato, and a thirty-second hamburger. But…
RAYTHEON TAPE: The Wonder Cooker was just too expensive for Joe and Jane Average so it was targeted to railroad dining cars, restaurants, and shipboard kitchens. But they weren’t selling like hotcakes. Even though they could make hotcakes in seconds.
TWILLEY: It took a couple decades, but eventually Raytheon decided to partner with Amana, a consumer appliance company, to make a version of their Radarange that was targeted at the general public
GRABER: Even though it was lower power, this new oven must have seemed pretty miraculous—baked potatoes cooked in minutes? And you put something inside, press a button, and nothing really gets hot except for the food itself and maybe the plate, no hot oven? How does this miracle box actually work? We called food science guru Harold McGee to find out.
HAROLD MCGEE: A microwave is essentially a radio transmitter but instead of broadcasting outward it broadcasts inward.
TWILLEY: Basically, that magnetron thing, it’s broadcasting short waves—microwaves—of electromagnetic radiation. And those waves are being reflected off the walls of the box and into the food.
CG And the prime target for those microwaves? The water in food.
MCGEE: And so what you’re doing when you microwave a food is you’re heating its water molecules.
TWILLEY: The thing about water molecules is that they are asymmetrical, in electrical terms.
MCGEE: So that when the radio field shifts, as it does many many times a second, it causes those asymmetrical molecules to shift at the same time.
GRABER: In fact, billions of times a second.
MCGEE: And what that does is cause friction which heats up the food. A microwave oven can actually vibrate and heat up the water molecules to a depth of about an inch into the food.
TWILLEY: This is very different from how an oven heats food. An oven can only heat up the food at the surface—by heating up the air around it.
MCGEE: And air is a very poor conductor of heat. So it takes a long time to heat things up.
GRABER: There are benefits to the oven’s slow cooking speed. First, it gives you a larger window to rescue your dinner if it’s slowly getting overcooked. But more importantly…
MCGEE: It’s a wonderful place to put foods if you want to get a crisp, crunchy, brown surface because air is dry. And the oven is very good at desiccating the surface of foods and allowing those browning reactions and flavor development to take place.
TWILLEY: Not to get all nostalgic for roast beef again but an open fire is actually even better at this. A regular oven works by conduction—so, heating air, which heats the food. A flame is pretty much pure infrared radiation. And that gives you the most gorgeous sizzling crust.
GRABER: Microwaves are good at getting water molecules really, really excited, which means those water molecules rub against each other and generate heat.
GRABER: So it’s great at, say, reheating soup.
MCGEE: But if what you want is that wonderful browned crust, it’s simply not going to give you that.
GRABER: No, no delicious roasting or baking or browning in the microwave.
TWILLEY: So one of the things that is really weird about microwaves is that your food gets sweaty in them, and that’s a problem.
GRABER: Actually, your food sweats in an oven, too.
MCGEE: Any time you heat a food with water in, it begins to cool itself off just the same way we do, by evaporating water from its surface.
GRABER: In an oven, that air is hot, and so the surface stays hot, too. But in a microwave, the surface sweats and cools down, but the water an inch in, it’s heating up and it can’t go anywhere.
MCGEE: So it turns out that you can actually burn foods on the inside easier than the outside in microwaves.
TWILLEY: There are other problems. These microwaves—they’re waves. So they have high points and low points. Which leads to the dreaded issue of hot and cold spots in your food.
GRABER: This is a big enough problem that there is a microwave scientist at Cornell University named Ashim Datta who is studying just this issue.
ASHIM DATTA: If you have a hot air oven with a fan, it kind of mixes and every place is close to the same temperature. That is fundamentally not the case in microwaves because you have these patterns of high electric field and low electric field.
TWILLEY: Ashim’s favorite way to demonstrate this problem to his students is with cheese.
DATTA: So you have a layer of cheese and you’ll see that someplace it melts and other places it doesn’t.
GRABER: But nobody was talking about or thinking about these types of problems when microwaves were first introduced to the public. These ads were all about the cooking revolution.
CAVEMAN MICROWAVE AD
SILVA: Well, the microwave oven! In the 70s, the microwave oven appears as the savior of the busy housewife.
TWILLEY: Elizabeth Silva has her own favorite microwave ad. It appeared in Good Housekeeping magazine in 1973. And it’s addressed directly at, yes, the busy housewife.
SILVA: Your husband is returning from a conference in 45 minutes. The chairman and his wife are accompanying him.
GRABER: But dinner is still unprepared. You would like to offer tomato soup followed by trout with new potatoes, peas and asparagus. And for dessert an upside down cake topped with peaches and cherries.
SILVA: Impossible until now. For today, in that time you can cook the meal of your choice, set the table, put the children to bed and get changed.
TWILLEY: Amazing. But once again, we’re talking about an innovation in cooking technology that’s also tied into its larger social context. At this point, in the 1970s, the issue is that the busy housewife—she actually now has a job, but gender roles have barely changed, so she’s expected to put dinner on the table for the chairman and his wife after a long day in the office. That’s the excitement behind the microwave’s introduction—saving time!
GRABER: And as a result, the microwave also is another step towards basically not needing any knowledge about cooking or food at all.
TWILLEY: Which had a curious kind of side-effect in terms of those gender roles and the question of who was doing the cooking.
SILVA: In many ways there is a democratization of the cooking process once brain power is put into the microwave. I call that the emergence of the stupid cook.
GRABER: Teenagers could cook, men could cook. But how much of this was really cooking? What the microwave is best at, as we’ve said, is just heating up food.
SILVA: And properly engineered foods in terms of size, in terms of texture, in terms of all of those things.
TWILLEY: And that properly engineered food, pre-prepared in small-enough, regular-enough chunks to not explode or heat unevenly—that kind of food was best made in a factory.
GRABER: This is of course the decade in which processed food is kind of taking over.
TWILLEY: Like Elizabeth says, the microwave is push-button stupid cooking. But the food is pre-prepared too. In combination, this kind of cooking could not be further from the woman using her hand to gauge the temperature before making muffins, or from Ivan Day’s sophisticated fire management for roasting.
GRABER: And there’s something else about this pre-prepared microwaveable food: it usually comes in a serving size of one.
SILVA: It does liberate people from eating together in many ways. It fits in with a more flexible, fluid way of living.
TWILLEY: Which again, is a long way a way from the fireplace as focal point—now we’ve not only lost our flame, we have a little countertop box making ready meals for one.
GRABER: But the microwave never became the most used appliance in the kitchen as those futuristic ads promised. Unlike the oven, which did totally replace the hearth, the microwave lives sort of alongside your existing oven.
TWILLEY: In reality, people almost never use their microwave to cook trout and new potatoes from scratch for the chairman and his wife.
MCGEE: One of I think the best uses for the microwave is reheating things that have already been cooked the way you want them to be. And you simply need to bring them back up to a desirable temperature.
GRABER: And the occasional bag of microwave popcorn.
TWILLEY: We’ve now brought the oven pretty much up to date in the modern kitchen. But there are a lot of people in the world who don’t cook in a modern kitchen.
MICHELLE NIJHUIS: Some 3 billion people are thought to use either pretty inefficient wood stoves or just open fires to cook their food.
GRABER: Michelle Nijhuis is a reporter, and she traveled to Guatemala to write about these wood stoves for National Geographic.
TWILLEY: Just as they were in 1600s England, these wood-fueled cooking fires are dangerous and dirty.
NIJHUIS: The estimate is that the typical cooking fire produces about 400 cigarettes’ worth of smoke every hour. So you can imagine over a lifetime or over a childhood particularly that that would have a pretty huge health impacts.
GRABER: That’s not the only problem with these inefficient wood-fired stoves. People cutting wood for stoves can lead to stripping hills and regions of their forests, which can lead to landslides and other environmental problems.
TWILLEY: Plus these stoves are sooty—the black carbon they emit is a major contributor to climate change.
GRABER: And when women and children have to walk farther and farther to find wood, they’re often not able to go to work or school.
TWILLEY: So this seems like an easy problem to fix, right? We’ve figured out ovens in the developed world, let’s just share that technology with these folks, and boom!
NIJHUIS: But what sounds like an easy fix is unfortunately much more complicated.
GRABER: NGOs have been working on this issue for about four decades.
TWILLEY: It really all got started after a huge earthquake in Guatemala in 1976. A bunch of major international aid groups came into the country to help rebuild.
NIJHUIS: And a lot of people, as they were helping families who had been affected by the earthquake, noticed that these families were dealing with these very smoky and inefficient stoves and thought, well, gosh, maybe we can fix this problem.
GRABER: So this cookstove replacement effort started in the 1970s, that’s about forty years ago. You’d think maybe they’d have fixed the problem by now and everyone would have great ovens?
NIJHUIS: You know, they’ve figured a lot of things out but they’ve run into a lot of unexpected obstacles.
TWILLEY: Some of these obstacles are the obvious challenges: how do you make something that is fuel efficient and not smoky and super affordable and portable?
GRABER: And then some are only predictable if you look at history—the people who use those smoky stoves today feel the same as folks in England did when they couldn’t cook their roast the way they wanted to. They’re used to cooking tortillas and tamales on a big flat surface over a fire.
NIJHUIS: No one wants to use a stove that doesn’t cook their staple cuisine perfectly. And the husbands will say this food doesn’t taste right or I can’t warm my feet in the morning like I used to. You know, stoves are at the center of a household—they’re really the heart of a household in many ways. You know, people gather in the kitchen, they warm themselves in the kitchen. And so it really gets at all these core family dynamics in a surprisingly deep way.
TWILLEY: These are exactly the kinds of things that British people complained about when they lost their open fires—they mourned their smoked sausages and roast beef and the loss of the focal point of their homes.
GRABER: Michelle got to experience the downside of those traditional fires personally. She spent Easter with the Perez family.
NIJHUIS: And since they were using this inefficient old stove to cook a large meal, the kitchen was just full of gritty smoke. And it was a really happy, wonderful scene. People were laughing and talking, but they were clearly affected by the smoke too. You know, it’s not the kind of smoke that you can get used to. I mean, people maybe used to the feeling but it’s never comfortable because it makes your eyes water, it’s really gritty and heavy.
TWILLEY: Michelle says her throat ached for days afterward.
GRABER: While Michelle was in Guatemala, she also spent some time with midwives who are trying to help families like the Perez family switch to cleaner gas stoves.
TWILLEY: And again, these efforts are encountering many of the same obstacles as gas-stove promoters did back in England in the late 1800s.
NIJHUIS: People were afraid the gas stove might blow up so they taught them about safety and how to make sure that their kids and their families would be safe. But perhaps most importantly they role played conversations with other family members.
GRABER: One woman would pretend to be herself talking to her husband, and another woman would play the husband.
NIJHUIS: And she’d be saying, oh, you know, little husband I need, I need money for the cylinder. And then, you know, her friend would come up with all these objections. Why do you need that new stove anyway? You know, why do we need that? Why can’t we just use the stove my mom does? And so they would go through these arguments and and apparently it worked really well. And not only that the women just have practice standing up for themselves but they also got clear in their own minds why they wanted to make this change.
TWILLEY: And there’s another trick that these international aid organizations have tried that seems to help with the transition. This one is straight from Count Rumford’s playbook.
GRABER: They set up storefronts run by local women where other women can come in and try out the stoves, see how they work, why they’re an improvement, get them comfortable with the idea of switching.
TWILLEY: Michelle hung at one of these storefronts, which turn out to be pretty popular.
NIJHUIS: Families came in together several times and talked with one another about what they liked and didn’t like.
TWILLEY: And surprise, surprise, people are more likely to use a stove that they’ve tried, and tested, and chosen themselves!
GRABER: But there are still billions of dirty, smoky inefficient wood stoves in use today—nobody’s solved this problem yet. Michelle says that aid groups are making progress, though, and they’ve come up with solutions that work best in different regions. It isn’t one stove fits all.
TWILLEY: But these things take time. Adapting to new cooking technology took more than a century in England!
NIJHUIS: And these midwives were saying it’s when the young couple is able to set up house separately or even in a separate little compound on the same property, when they have control over their kitchen, that’s when we see change happen. And that’s when we see healthier kitchens.
GRABER: This change will probably take a generational shift. Because if there’s one thing that we can learn from the history of ovens, according to Sara Pennell, it’s that change is hard.
PENNELL: There’s so many facets to it that I think it’s not just simply about, oh, well, this new technology exists and on paper it should be widely adopted because it does x, y, and z. But we know that that doesn’t happen. We know it doesn’t happen in the past and therefore we should sort of be a little bit more humble in thinking, well, why might it not be something that people want to welcome with open arms.
TWILLEY: The history of changing cooking techniques can help keep us humble. It can also give us good ideas to help with that adaptation—like this idea of demonstration kitchens. But, at the end of the day, the thing that really makes a new kitchen technology succeed? It has to fit with larger changes in society and culture.
GRABER: In the past, one of those changes was urbanization—and an easier access to gas pipes. Also changing gender roles. And this is what those midwives are also pointing out—as gender roles are changing among the younger generation in Guatemala, they’re more willing to try something new in the kitchen.
NIJHUIS: You know, so often I feel like the stereotypical environmentalist coming from the developed world to the developing world is trying to get across the message of don’t do what we did, do as we say not as we do. Because, you know, in the developed world we have this history of using up all our resources. And then once we have no other option finding some innovation.
TWILLEY: And so these international organizations are coming into communities that, yes, are experiencing some problems, but are not yet being forced into change by larger social, environmental, infrastructural, and cultural shifts.
NIJHUIS: And they’re saying well, I know we’re strangers and I know we don’t understand how your lives work but could you just trust us and try this new stove and see if it improves your lives at all? And it’s no wonder that that’s a very complicated.
TWILLEY: Guess what, the story of how we heat our food and the technology we use to do that—that’s only half the story.
GRABER: Next episode, we are exploring the other half of this story: pots and pans.
WILSON: I think pots first of all led to cuisine itself. To me, it’s the great beginning of cookery.
GRABER: Thanks this episode to so many wonderful guests: Bee Wilson, Sara Pennell, Harold McGee, Elizabeth Silva, Michelle Nijhuis, and Ashim Datta. We have links to their books, articles, and research on our website, gastropod.com. Also, huge thanks to our volunteer Ari Lebowitz who helped with research this episode.