Water temp guage

While we're on the subject of guages, does anyone know what substance the
reservoir bulb on the water temperature guage contains? Is it ether or
alcohol? Is it something I can obtain to repair a couple of my guages? I
have repaired these units before, but only if the were reconnected before
they were run up to operating temperature. A couple I have were by DPO's.

TIA

Gerard



G G              Gerard Chateauvieux
 E A
  R R        pixelsmith@gerardsgarage.com
   A A
    R G          Pixelsmith  on  Duty
     D E
      S      http://www.gerardsgarage.com