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Perfection in Convection: Your Oven’s Temperature is More Art than Science

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Your oven’s temperature may be far more volatile than you realize.

As you might imagine, we at Dickson believe that temperature is a critical variable to monitor in our daily lives. Society as a whole measure our homes, our workplaces, our fridges, and, of course, the weather.

The devices for measuring these readings often vary, and you may  get several different readings using several different thermometers for the same application. One example involves the ovens we use in our homes. Brian Palmer from Slate discusses in detail just how illogical this often is.

“For most of human history, bakers had very little control over the heat of their ovens and hearths, and they knew it. The earliest ovens were giant pits filled with hot coals or burning wood, and though technology improved over the millennia—brick or ceramic chambers eventually came into fashion—the basic concept remained the same through the beginning of the 20th century. As a result, estimating oven temperature was more art than science.”

What that ultimately means is that heating instructions in a recipe are more like guidelines than harsh requirements.

“When you set an oven to 350 degrees, there isn’t a single spot inside of it that stays at 350 degrees for the duration of a bake session. The modern gas or electric oven has an automatic thermostat that, by design, lets the temperature drop a predetermined number of degrees below your chosen temperature before switching the heat on. The heat then surges the oven well past the desired temperature before shutting off again. A 350-degree residential oven is designed to stay between around 330 and 370 degrees—and that’s if it’s well-calibrated, which few ovens are.”

This also struck a chord of curiosity with many of us in the office as the annual celebration of hearth and home grows nearer, so we decided to run an experiment to test different ovens we own throughout the office to understand just how reliable and trustworthy they may be. We tested the accuracy of the oven’s actual temperature versus the temperature the oven was actually supposed to be set at based on the display on the oven. For the purpose of the experiment we used our cloud based DWEs to monitor the temperature of the oven and report data back to the system in a single account so we could easily analyze everyone’s data in one place.

To create comparison data against all of these variable we set a variety of escalating alarms. Each would go off when the oven held a consistent temperature at each stage of the process for 20 consecutive readings.

    1. Temperature > 300 for 20 readings (approx 10 minutes)
    2. Temperature > 350 for 20 readings (approx 10 minutes)
    3. Temperature > 400 for 20 readings (approx 10 minutes)
    4. Temperature > 450 for 20 readings (approx 10 minutes)
    5. Temperature > 500 for 20 readings (approx 10 minutes)

Should the alarm trigger, we would increase the temperature of the oven an additional 50 degrees. If the oven never reached the proper temperature within 15 minutes, we advanced to the next stage. Not only did the results vary by oven, but they were more extreme than we’d even expected.

Scott’s oven performed most in line with what we had expected based on what you’ve already read. The oven’s thermostat got the oven up to temperature and then quit heating until the temperature dropped too dramatically, and then the process started anew. What that means, is that the oven wasn’t consistently over 300℉ for ten minutes until after the oven had been increased from 300℉ to 350℉. This same failure occurred at every step in the test.

George’s oven was much more consistent in holding its temperature, but it still required, in most circumstances, an increase in temperature to reach the previous setpoint’s alarm. Based on this graph, it would be safe to say that the inside of the oven also held temperature much better than the others in the test.

Matt’s oven may have been the most bizarre. His 350℉ alarm ended up going off at a lower actual temperature because his oven did such a poor job at holding an ongoing cooking heat. While there was less variation from step to step, it poorly reached the temperatures, and held the temperatures, expected from the user.

Ryan’s oven was the only one that hit it’s expected temperature, consistently, at the 300℉ mark. While it looks most similar to Scott’s chart, It had a much smaller amount of variation throughout the experiment, suggesting his oven, of the four, was most reliable for cooking.

As you can see from our tests, an oven’s temperature isn’t reliable. Not only do ovens not always reach their expected temperature, but rarely do they hold them or even match what they say, let alone show consistency between models. From a mean kinetic temperature standpoint, a simplified way of expressing the overall effect of temperature fluctuations, there was nearly a 20°F difference between the ovens in testing. It means that cooking that Thanksgiving feast requires more than just putting it in and forgetting it. It means you need to be hyper vigilant to your meal. Otherwise you could end up with dangerously undercooked food or a meal so overdone it’ll have to swim in grandma’s gravy to be edible.

The reliability of the consistency of temperature within the space notwithstanding (it’s the reason we recommend mapping your facility, cold storage, chamber, or warehouse prior to finalizing any system you plan to set up), the fact is that many thermometers, like those in ovens, aren’t well calibrated. We understand just how critical it is for accurate and reliable monitoring, especially considering we’re a company that owes its existence primarily to the monitoring of temperature.

It’s why we have an on-site calibration lab to ensure the accuracy of our products. The way the calibration process work depends on your need, but all devices are calibrated with the same process. Dickson’s calibration lab will compare a device (unit under test) with a more accurate device (the standard). The standard tells us exactly where 70°F, 0°C, 137°F, etc. are. After the comparison is made we adjust the device under test so it reads the same as the standard.

The obvious question from there is, who gets to say that our 70°F standard is the standard? Well, it’s the same group that says a yard is a yard, an ounce is an ounce and a joule is a joule; the National Institute of Standards and Technology, or NIST for short. This government agency creates and maintains standards of measurement for length, mass, time, etc. In regards to temperature, standards are sent in by manufacturers, and those standards are calibrated to an even more accurate standard. They then become a NIST certified standard, which the Dickson calibration lab then uses to calibrate your device. It means that while you may not be able to trust your oven, you can trust your monitoring device. That’s something that’s critical for all.

 

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