The Best Way To Thicken Tomato Sauce Without Changing The Flavor - Chowhound

Although it depends on everything from the surface area of the sauce to atmospheric pressure and humidity, water generally evaporates at a rate of 1% to 2% per minute at a vigorous boil. It will take approximately an hour to boil off a liter of water. It's very unlikely you'll need to boil off a whole liter of water, so this process won't take an hour, but how long it takes will depend on how much sauce you have…