Does Water Evaporate Faster With the Lid On or Off?

Boiling water for any number of recipes can be done with the lid on or off, and while people are not usually in a hurry to cook their dishes, many of them still wonder if the water they’re boiling will evaporate faster with the lid on or off.

Water in a pot with the lid off is always going to evaporate faster. Water evaporates faster when the air pressure is just right and there is nothing to keep the heat in the pot. More and more heat will dissipate into the air the longer you boil the water without a lid.

The Basics: Evaporation vs. Boiling

Water boiling in pot after chef learned if water evaporates faster with lid on or off

While boiling water without a lid helps the water evaporate faster, the same isn’t true when you’re just trying to get the water to boil. In fact, if you want your water to boil faster, it’s best if you boil it with the lid on.

As far as evaporation is concerned, keep in mind that water being heated in an open pot without a lid loses some of the energy that could be raising the temperature of the water. When you put a lid on the pot of water, the water vapor is prevented from escaping and therefore the temperature rises a lot faster.

So can you make your boiling water evaporate a little faster? You can if you spread the water over a large area, then apply heat very evenly. This makes sense when you think about it. The lid will keep air out of the pot and will keep the heat inside the pot, but since it takes both air and heat for the water to evaporate, leaving the lid on means that the water is going to evaporate at a much slower pace. When hot air is used to make water evaporate, it increases velocity and therefore it increases the speed of evaporation.

Evaporation 101

Pot of boiling, steaming water set up after chef learned if water evaporates faster with the lid on or off

What if you want your water to evaporate faster but you don’t want to boil it? Here’s something you can try. First, place the water in a shallow tray so that the surface area is increased. Then blow warm air over it with a fan. You do this because warm air holds more moisture than cool or room-temperature air. Next, you’ll want to put your water in some type of metal container that has good thermal contact with its surroundings. Why? So that as it evaporates, it will not cool down any.

And if you’re wondering how long it takes boiling water to evaporate, here is your answer: If you’re boiling one cup of water, it will take a little over an hour for the water to completely evaporate.

Boiling Water: Lid or No Lid

People have conducted studies on the amount of time it takes for water to boil with and without a lid, and the differences went like this:

  • When a pot with no lid was used, the water inside the pot took about six minutes and 47 seconds to reach the boiling point.
  • When the same thing was done with the lid on, it took the water five minutes and 46 seconds to reach its boiling point. In simple terms, this means that water boils about 16 per cent faster in a pot with a lid on it.

Of course, this also proves that you can still boil water without a lid if you wish. It’ll take a little longer, but it still happens. Water boils once it reaches its boiling point (duh), and it reaches that point a lot faster when the water is being boiled in a pot with a lid on it.

Water Pressure Also Matters

When you’re boiling water, the rate of evaporation depends on many things, including the amount of heat loss, the air pressure and the water pressure. The heat energy changes based on all three of these things, and when the lid is on, the pressure and energy underneath the lid both increase.

These are just a few of the reasons why water boils faster when the lid is on and why it evaporates faster when the lid is off. The amount of time varies depending on whether the lid is on or off, but in the end it doesn’t vary a whole lot.