How do I fix a glass thermometer?

Written by alex burgess Google
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How do I fix a glass thermometer?
Some glass thermometers are repairable if you follow basic safety precautions. (thermometer image by Friedrich-W. Gärtner from

Analogue glass thermometers are sealed units that are repairable in certain circumstances. Coloured alcohol is the liquid used in modern glass thermometers; mercury thermometers are being phased out. It is dangerous to try to access the liquid contents of a mercury thermometer. Mercury is highly toxic, and you should not handle or inhale it.

If there is any sign of leakage from a thermometer, do not try to fix it. Always make sure the glass casing is intact before attempting to repair a glass thermometer.

Skill level:

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Things you need

  • Magnifying glass
  • Safety gloves
  • Safety goggles

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  1. 1

    Put on the safety gloves and goggles. Carefully check the outer glass casing for cracks or chips, using a magnifying glass if necessary. If the glass is cracked or damaged, do not attempt to fix it. Instead, dispose of the thermometer safely and legally.

  2. 2

    Look for signs that the thermometer has leaked, such as staining around the bulb area where the liquid is stored. If there is any possibility that a mercury thermometer is leaking, do not attempt to fix it. Call your local garbage service or household hazardous waste facility for advice on disposing of the thermometer safely and legally.

  3. 3

    Check the display. When liquid separates in a thermometer, it gives a false reading because of the air bubbles. If there are gaps in the line of liquid, it may be possible to fix this problem.

  4. 4

    Hold the thermometer securely, with the bulb end pointing away from you. Flick the unit away from your body sharply, just once, without letting go. The centrifugal force will pull the liquid back toward the bulb, so that it can give an accurate temperature reading again.

    Check the liquid in the display to make sure that the gaps are gone and there is an unbroken line from the bulb of liquid along the display. Repeat the process once more if necessary.

  5. 5

    Hold the thermometer about a foot above the floor, over a carpeted area or cushion, and drop it straight down without any additional force, bulb end first. This will force the liquid back together if the flicking method does not work. Be very careful not to drop the thermometer onto a hard surface, or let it bounce away from the soft surface.

Tips and warnings

  • Be extremely careful when shaking the thermometer to realign the liquid display. Make sure you are standing away from other people, and there is no danger that you are going to let go of the thermometer or hit something with it.
  • Never apply blunt force directly to a glass thermometer, as the casing will shatter.
  • Do not throw thermometers away with normal household garbage. They must go to household hazardous waste centres, or other facilities that accept hazardous waste.

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