General Precautions And Care

  • For safety and hygiene make sure to clean your flask with warm water and washing-up liquid before first use.
  • Do not look directly into flask when filling with hot liquids, rising steam can blind you.
  • For best results, pre-fill your flask before you use with either hot water for hot drinks, or cold water for chilled drinks. Let it stand for about 5 minutes before pouring out and filling with your choice.
  • Never use a microwave or conventional oven to pre-heat your flask.
  • Don’t overfill your flask. Leave sufficient space in the neck to fit the stopper. Fill to about 1 cm below the brim for optimal performance.
  • After filling, always ensure that the rubber seals on the lid are intact and that both the outside cup and stopper are tightly closed to ensure no spills..
  • Ensure that the flask stays upright to avoid leakage.
  • Do not stir the contents of a flask with a metal object, this can damage the liner and lead to the flask failing.
  • Do not store dry ice or any fizzy drink in a flask as they can cause the stopper to be forcefully ejected or break a glass liner.
  • Take care when using a flask for keeping milk products or baby food warm or cool as there is a possibility of bacterial growth.
  • Tea should be strained before pouring it into a flask.
  • Keep your flask away from direct heat to protect any plastic material and seals from damage.
  • If your flask has not been used for some time, rinse with warm water to remove residual odors.

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Cleaning Your Flask

  • Do not immerse the flask in water while washing.
  • Use warm water and washing-up liquid to clean your flask after use. Use a soft brush if you need to scrub. Rinse thoroughly with hot water. Dry thoroughly after leaving it to drain and store with the stopper off.
  • Never put your flask in a dishwasher. (Unless it is indicated as dishwasher safe, and then only after carefully reading the manufacturer’s instructions.)
  • To remove difficult stains fill your flask with hot water, add one teaspoon of bicarbonate of soda. Do not put stopper on while using this cleaning method. Soaking overnight produces the best results. Rinse before re-using.
  • Avoid abrasives, solvents and bleach products. Damage to the inner surface of the flask can weaken it and cause an implosion, especially with glass flasks.

 

 

Special Precautions With Glass Flasks

Glass flasks are less popular than previously mostly because they are prone to breakage and required special care.

  • The base of a glass flask is often screwed on and there are flanges on it that serve to space the liner and support it. Without the base, the glass liner can come loose from the neck, so always ensure that the base is securely tightened. This happened to a glass flask I owned. It got jammed into a picnic basket in such a way that the plastic was distorted and the base popped off. When I lifted it out, the weight of the full flask was too much for the glue at the neck and Humpty Dumpty had a big fall.
  • If a glass flask is dropped, the glass liner may break. It should be checked thoroughly for damage. In case it falls, do not consume the liquid inside, as it may contain small glass particles even if the liner is still intact.
  • Due to the breakage risk, glass flasks are not suitable for use by children.