A flask is an item, often metal, that can hold a liquid. It can be a stand-alone flask or part of a Thermos. Typically, it is used to keep things such as soup, coffee, tea and the like warm for an extended period of time. They are used for taking lunches or drinks to work or school. A stand-alone flask may be used to keep warm a drink such as a Hot Toddy. Still, over time, they will lose their heat. Luckily, there are methods that may extend the amount of time a flask will keep your liquid warm.
Fill your flask with hot water from your faucet. This will pre-warm the flask and prevent cold metal from cooling the liquid that it will soon contain. Place the cap on the flask.
Warm the liquid to its desired heat in a pot on a stove. Some foods or beverages may require boiling, others just simply need to be heated slightly.
Remove the cap and pour the water out of the flask. Be sure that the water has had enough time to warm the flask before it is removed. The body of the flask should feel warm.
Pour the liquid that has been heated on the stove into the flask.
Replace the cap on the flask. Turn it clockwise to tighten and secure it in place.
Purchase a cosy that will fit your flask. A cosy is a foam sleeve that can keep a beverage warm or cold. They can be found at many stores and online often in the drinks or summer supply sections. Commonly, they are called "beer" cosies and are even sold in liquor stores.
Warm the liquid that is to be placed in the flask. Boil the liquid on a stove or heat it in the microwave. Allow it to reach your desired temperature. Make it a little hotter if you will not be consuming it immediately as it will cool slightly over time even with a cosy.
Pour the liquid into the flask. Remove the cap by turning it counterclockwise with your hand. Pour in the liquid. Replace and tighten the cap by turning it clockwise with your hand.
Slide the flask into the open end of the cosy until the bottom of the flask rests on the interior bottom of the cosy. Keep the flask in the cosy to keep the flask warmer for longer.