The liquid in glass column thermometers separates – it’s natural. Store your glass column thermometer with the bulb end down, if possible.

Two methods for recombining the liquid in the column are:


  1. Fill a container with shaved ice and salt.
  2. Place the thermometer in this ice water bath, holding the thermometer upright.
  3. When the liquid goes back into the bulb of the thermometer, remove it from the water bath and swing it back and forth in an arc with the bulb down. This allows any trapped gas to rise above the liquid column and recombines the liquid column.
  4. Repeat if necessary.


  1. Place a pan of water over low heat.
  2. Hold the glass column thermometer in an upright position and immerse the bulb in the water.
  3. SLOWLY heat the thermometer bulb using the water. Caution: Do not heat too quickly or the bulb could break.
  4. Gently tap the thermometer column to allow the gas separating the column to rise to the top, thus allowing the column to recombine.