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One should cover a pan while heating?

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One should cover a pan while heating

Cooking abounds with old sayings and proverbs, which are sometimes useful tips and sometimes myths. We learn or hear them somewhere, and often trust them completely, even when they're wrong.

I propose simply to verify them, to see whether they are real useful tips that we can use, or just ill-founded popular beliefs.

Of course I can't claim to be writing scientific facts here, just personal observations and what I understand them to mean.

The belief

"One should always cover a pan while heating, so that it boils faster".

In other words, if you heat water (or something else), it comes to the boil faster with a lid on the pan than without.

The approach

We are going to heat 1 litre of water in an uncovered pan and measure the time it takes to boil , then another litre in a covered pan, heated and measured in the same way.

Comparing these times will tell us if it is really necessary to cover the pan.

Let's check:

1 litre of water is measured and poured into a pan without the lid and put on the hob with a thermometer in it.

Starting temperature of water (and room): 70°F (19°C).
step #1
The heat is switched on. The water reaches 210°F (100°C) in 9 minutes and 30 seconds.etape2
to allow it to reach room temperature again.

Another 1 litre water is put in the same pan covered with the same thermometer in it, on the same hob.

Starting temperature of water (and room): 70°F (19°C).
The heat is switched on. The water reaches 210°F (100°C) in 9 minutes and 27 seconds.etape4
The result is shown more clearly in the diagram: the temperature of the uncovered pan in red and that of the covered pan in green.etape5


The time difference is too small to be significant. It really doesn't matter whether the pan is covered or not.

So, "One should always cover a pan while heating, so that it boils faster." : False.

Last modified on: February 27th 2015

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Your 1 comments or questions on this page:

This is going to be a most interesting addition to your site, jh. Now I wonder if hot water or cold water makes any difference in the boiling time?
By Louise october 24th 2009 at 17:48 (n° 1)
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