The article footer implies that he's some kind of cooking science wizard, but I have trouble believing that Nathan Myhrvold has ever done more with an oven than toss a slab of meat in it. I'm no expert, but I've baked an awful lot of cakes, cookies, breads, and pastries, and I find this article very confusing:
Most of us bake, roast, and broil our food using a technology that was invented 5,000 years ago for drying mud bricks: the oven. The original oven was clay, heated by a wood fire. Today, the typical oven is a box covered in shiny steel or sparkling enamel, powered by gas or electricity. But inside the oven, little has changed.
Weird condescension towards "brick dryers" is a running theme of this article. To see how ridiculous this is, I invite you to consider a nineteenth century cake recipe with its many methods for determining correct oven temperature and shielding parts of the cake from the oven walls so that it bakes evenly. Turning a knob to set an arbitrary temperature, while imperfect, is a *vast* technological improvement over wood-fired ovens. (Remember: just because it's analog (or non-electronic!) doesn't mean it's not technology.) Likewise, the metal that the oven is made from represents thousands of years of technological advances in itself.
Preheating always seems to take an unreasonably long time because ovens waste most of the hot air they generate. The actual amount of energy required to reach baking temperature is quite small: Just 42 kilojoules will heat 0.14 cubic meters of air to 250 C. The heating element in a typical domestic electric oven supplies this much energy in a mere 21 seconds. Unfortunately, the heat, which originates in the heating coils of an electric oven or the burner of a gas oven, must pass through the air to get to the walls, and air is an awful conductor of heat, only slightly better than Styrofoam. Even worse, air expands when heated, so much of it flows out of the vent, heating the kitchen rather than the oven.
But the oven walls will heat the air anyway, so how much energy would we really save by heating the walls directly? Pre-heating is only a fraction of the oven's total operating time. And wouldn't an electric burner also produce radiant heat? And then a few paragraphs later:
As soon as you open the oven door to adjust or check on the food, nearly all the hot air spills out. The puny electric element or gas burner is no match for such large surges of cool air, so the temperature in the oven plummets, and it recovers slowly.
which is totally inconsistent with what he said earlier.
At 200 C or below, convection moves most of the heat. But at 400 C, radiant energy starts doing a fair amount of the heat transfer. At 800 C, radiation overwhelms convection. Why couldn’t we have an oven designed to cook primarily by convection at low temperatures that switches to radiant heating for high-temperature baking?
As others have mentioned, this is a Fahrenheit/Celsius error at best and a non-sequitor at worst. The highest normal baking temperature is around 500 F (260 C) unless you're going crazy with pizza. If the article's numbers are correct, we should totally ignore radiant heating! (I don't think they are.) And I'm not clear on how the oven is supposed to "switch" to radiant heating. If the walls are hot enough to radiate, you get hot air for free. If the air is hot, it heats the sides of the oven.
Myrhvold next dives into a laundry list of suggested improvements, which fall into a few categories:
1. Stuff that already exists, but is expensive.
2. Stuff that's not done because it's too expensive and/or inconvenient.
3. Complicated gimmicks that require recipe-specific behavior.
4. Star Trek.
And you’re not going to be able to stop a cook from opening the oven door on occasion ... But designers could prevent that blast of cold air by building a blower into the door frame that generates a “curtain” of air whenever the door is opened, retaining more of the preheated air in the oven. ... Designing one for an oven is trickier because the chamber is small and turbulent currents could do more harm than good. Still, it could be done.
Personally, I haven't found the occasional door-opening to be a big deal. It is discouraged for delicate foods like cakes. But clearly we need a complicated, expensive air curtain that either runs constantly or turns on in an instant. Nobody knows how to do it and it might be more trouble than it's worth, but Myhrvold is *sure* that someone (not him) will make it work.
I'm going to skip most of the broiler stuff since I don't broil, but a couple things stood out:
Electric broilers use bars or rods made from Nichrome, an alloy of nickel and chromium (and often iron) that heats up when electricity passes through it. With reasonable energy efficiency, electric broilers can heat quickly and reliably to temperatures as high as 2,200 C. Maximum settings are typically restricted to 1,200 C in order to extend the life of the heating element and avoid charring the food.
Nichrome melts at around 1400 C (2550 F). I strongly suspect this is another unit error.
You can make a broiler cook more evenly with a simple DIY project: Install some shiny vertical reflectors near the edges of the compartment. Another good way to ensure that food browns evenly under a broiler is to wrap the dish with a reflective foil collar. But why should you have to jury-rig a fix? It wouldn’t be hard for oven manufacturers to build reflective materials into the oven. Viking Range is developing stainless steel cavities that are more reflective, but they need better materials that are easy to clean and don’t discolor when heated to high temperatures.
Not sure if I should be more bothered by the idea of removing tarnish from my oven in order to cook, or "all it needs to work is a major advance in materials science".
But technology offers a fix here, too. Oven designers could put optical sensors in the oven chamber... And a camera in the oven could feed to a color display on the front panel ... a decent optics system ...
Let's talk about what "in the oven" means for electronics -- 250 C. Consumer-grade electronics stop working about 85 C (at best). Higher-grade stuff can go up to 125 C. Beyond that you're talking about serious high-reliability components. Maybe he wants some kind of fiber-optic feed? But that doesn't sound like "a decent optics system". And again, there's more cleaning, which nobody likes.
Even when perfectly calibrated, however, the standard oven thermometer has a big problem. Water evaporating from the surface of the food carries away heat, leaving the food cooler than the surrounding air. Scientists call this temperature at the surface of the food the wet-bulb temperature (that is, the dry-bulb temperature minus any cooling by evaporation). The lower the relative humidity, the more evaporative cooling, so the greater the difference between the two temperatures.
Because most of the humidity in an oven comes from the food, adding food to the oven raises the humidity and, therefore, the wet-bulb temperature at the food’s surface. This means that bigger batches bake faster. Did you burn the holiday cookies last year? Blame your oven’s ignorance of its own humidity.
Cookie dough is usually very dry. The water comes from the butter and the eggs. I know he's looking for something everyone makes as a rhetorical device, but it's still a sloppy and misleading example.
And while you’re at it, perhaps you could solve a related problem: the inadequate precision of the humidity- and temperature-control systems. Both temperature and humidity levels stray from the set points more than they should.
That's an obvious cost saving. It's a solution to a different problem.
Finally, Myhrvold reaches the place where he should have begun:
Some other interesting technologies that make ovens more useful are already on the market. Newer models of steam ovens by Wolf Appliance
This is where the article loses me. Convection ovens with steam injection are far beyond "brick dryers". They're also only a few thousand dollars, which is expensive but within the reach of a hobbyist. *This* is the state of the art in home ovens. Why did we start with low-end household models? People use those because they're cheap or because that's what their landlord provided, not because they're good. Nobody's going to get any of Myhrvold's fantasy features without massive cost reduction. So is this a speculative article about the furthest reaches of oven technology, or is it about practical ways of improving oven design? Despite tap-dancing past major technical obstacles, the article doesn't claim to speculate. From near the beginning:
Yet oven manufacturers could solve every problem with existing technology, if only they would apply it.
But on the practical side, here's the only mention of increased cost in the article:
An oven could be manufactured today that could incorporate many of the technologies now available and go a long way toward turning today’s mere brick dryer into a true food cooker. It would have wet- and dry-bulb temperature controls, better thermostats, probes to go inside food, and sensors that detect hot and cold spots. All these features would add just a few hundred dollars to the cost of the parts.
I don't know where he got that number from, given that each one of those features is only found in a commercial oven that costs thousands of dollars more than residential models. Regardless, even his lowball estimate is doubling the price of a cheap residential oven. And some of these new features are complicated for the user and break backwards compatibility with existing recipes.
Maybe I'm being too hard on the guy. I should probably have more patience with this sort of breathless "more electronics solves every problem!" attitude, especially since it helps keep me employed. But more electronics won't do anything about my landlord, and that, not theoretical oven design, is the biggest problem with most people's kitchen appliances.
(I still can't get over the "brick dryers" thing. Brick making is a big deal! Has Nathan Myhrvold done anything in his life as useful as making bricks?)
