What's Cookin'?
Congratulations! If you have made it here, you may have been lucky enough to snag one of our snazzy Metharc kitchen timers.
Having found yourself in this fortunate position, you most certainly now want to boil an egg. Fear not – we can help.
- Bring a saucepan of water to a boil.
- Slowly lower in your eggs using a spoon or strainer, and dip in and out two times to prevent the cold shells from cracking with the extreme temperature change.
- Lower the heat to maintain a simmer and cook to your preferred doneness, using this handy image of eggs as your guide and your new timer to keep track of the time. If your eggs were fridge cold you may want to add around 1 minute to these recommended cooking times.
- Take out the eggs as soon as they’re done and run them under cold water or put them in a bowl of cold water and ice to stop the cooking and make them cool enough to peel.
But wait, is it always that simple?
No its not 😊. These cooking times apply if you are at or near sea level. At elevation, cooking times will be longer. Why is that, you may ask.
To answer that question it is useful to consider the phase diagram of water. A phase diagram is a chart that displays the relationship between temperature, pressure, and the physical states of a substance (solid, liquid, gas) under different conditions. It shows the specific conditions where phases coexist, such as the boiling point, melting point, freezing point or sublimation point. A phase diagram typically includes:
- Phase boundaries: Curves that separate different states (solid, liquid, gas), indicating where a substance transitions between phases.
- Triple point: The condition where all three phases (solid, liquid, and gas) coexist in equilibrium.
- Critical point: The end of the liquid-gas boundary, beyond which a substance becomes a supercritical fluid with properties of both gas and liquid.
Phase diagrams help in understanding the behavior of substances under varying environmental conditions.
In our case, since we are using water to boil our eggs, the phase diagram of water (as shown) becomes important, and the following important features can be noted.
- The slope of the line 2 separating the solid and liquid regions is negative; this reflects the unusual property that the density of the liquid is greater than that of the solid, and it means that the melting point of ice decreases as the pressure increases. Thus if ice at 0°C is subjected to a high pressure, it will find itself above its melting point and it will melt.
- The dashed line 1 is the extension of the liquid vapor pressure line below the freezing point. This represents the vapor pressure of supercooled water – a metastable state of water which can temporarily exist down to about –20°C.
- 3 The triple point (TP) of water is just 0.0075°C above the freezing point; only at this temperature and pressure can all three phases of water coexist indefinitely.
- 4 Above the critical point (CP) temperature of 374°C, and 220 bar pressure, no separate liquid phase of water exists, it has entered a supercritical state.
Phase Diagram of Water
(Ref: https://learn.saylor.org/mod/page/view.php?id=51399)
But we have digressed. Let’s get back to the task at hand – boiling an egg at altitude 🌄. From the water phase diagram above it can be seen that as the atmospheric pressure decreases (as it does at altitude), the boiling point (transition from liquid to vapor phase) of water also decreases. This means that water boils at a temperature lower than 100°C. In fact, it drops by approximately 1°C for every 300 meters above sea level, and the cooking time will have to be increased to reach the same doneness level.
The adjusted boiling time can be calculated using the formula below.
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