If the mercury (or other indicator fluid) column of a thermometer separates, the vacuum in between will make the temperature indication inaccurate. Here are some ways to remove the vacuum from the column. Please read all the steps before trying.
Steps
Step 1. Inspect the thermometer for damage
Do not use it again if it has cracks or is damaged in any way. It has had its day and must be disposed of properly (see Warnings below).
Step 2. Write down the indicated temperature
Step 3. Choose a method to reset the mercury that has separated
Method 1 of 4: Cool down
This is the easiest way to fix the bollard. Note, however, that this method can give different results.
Step 1. Put the thermometer in the fridge or, better yet, in the freezer
If it's cold enough, this should send the mercury (or any other indicator fluid) into the bulb with nothing else to do. See the next steps if you don't have a fridge or freezer available or if it doesn't work.
Method 2 of 4: Reheat
This method can take several attempts.
Step 1. Put the thermometer in the sink
Step 2. Gradually heat the bulb with a hot blow dryer
The mercury will rise to the top of the thermometer, gathering all together.
Step 3. Let it cool down to room temperature
Step 4. If you have to try several times, heat and cool gradually
Do not heat it too much, otherwise the thermometer may explode.
Method 3 of 4: Shake
This method is quite reliable, as it was used in hospitals and similar places before electric thermometers and other alternative systems arrived. However, there is a risk of losing your grip while shaking the thermometer, causing it to break and lose the mercury.
Step 1. Firmly grasp the thermometer near the top so that the bulb containing the mercury (or other indicator liquid) points down
Step 2. Quickly shake the thermometer from top to bottom with sharp flicks of the wrist
Step 3. Check the indicated temperature
If the indicated temperature has dropped since the last check, continue to shake the thermometer down. You may have to do this several times before the void in the column disappears.
Method 4 of 4: Drop
This method appears to have the best results, but it also risks breaking the thermometer if it falls too high or onto a hard surface.
Step 1. Hold the thermometer vertically - with the bulb pointing down
Step 2. Drop the thermometer onto a bed, pillow or even a folded towel so that it is at least 8 times thicker than when lying down
More than one or two falls are not recommended.
Advice
- Store the thermometer horizontally or upright with the bulb at the bottom. Never hold it upside down (with the bulb on top).
- Don't forget to wash your hands!
Warnings
- Consider no longer using a mercury thermometer if you use it for cooking or for medical reasons. Since mercury is very toxic, using it in food or on the body is not recommended. New electronic thermometers and those that use a mixture of red dye and alcohol are safer and clearer.
- Don't just "throw away" a tool that contains mercury. Mercury is a heavy metal, and it is highly toxic. In many places, it is illegal to improperly throw away mercury. Take it to the municipal landfill and ask them where to throw away thermometers or other tools that contain mercury. Never mix mercury-containing tools with common garbage.
