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Why a roast keeps getting hotter after you take it out: carryover cooking and the heat still on its way in
You pull the roast at 60 °C, and five minutes later the probe says 66 °C. Nothing is heating it, so where did the heat come from? The answer is that an oven…
Why a microwave leaves cold spots: a standing wave 12.2 cm long, and a chocolate bar that measures the speed of light
Microwave ovens fill a metal box with radio waves 12.2 cm long. The waves bounce off the walls and add up into a standing wave, a frozen pattern of hot spots…
Why honey never spoils: it isn't the sugar, it's the missing water
Honey is rich, sweet and nutritious, so why don't bacteria and moulds move in? Because microbes need free water, and honey's sugar holds almost all of it…
Why bread rises: yeast only inflates the bubbles your kneading put there
Yeast doesn't blow bubbles into dough. It only inflates the ones your kneading already folded in. That means the number of bubbles is fixed early, and the…
Why salt makes ice cream freeze: ice melting below 0 °C pulls out the heat
Ice is already at 0 °C, so how can a handful of rock salt make it colder? Because salt makes ice want to melt below 0 °C, and melting costs energy: about 334…
Why oil and water mix in mayonnaise: an egg yolk coats every droplet
Oil and water refuse to mix, yet mayonnaise is about two-thirds to four-fifths oil and holds its shape on a spoon. One egg yolk does the work: its molecules…
Egg yolk sets at a lower temperature than the white. So why is it runny?
An egg yolk sets at about 70 °C. Most of the white needs about 80 °C. So why does a soft-boiled egg come out with a firm white and a runny yolk? Because…
Stale bread isn't dry: its starch has quietly turned back into crystals
Bread left on the counter turns hard and crumbly, and it looks like it dried out. It mostly didn't. In 1852 Jean-Baptiste Boussingault showed that bread sealed…
Why popcorn pops, and why some kernels never do
A popcorn kernel is a tiny, sealed pressure vessel. Its hard shell traps water inside the starchy core until heat turns that water to steam, and pressure…