Ambient Weather WS-B1025C Storm Glass

This is an Ambient Weather WS-B1025C reproduction storm glass.  ​It is a sympiesometer, more commonly called a tendency barometer today.  It uses Boyle's Law, which was discovered in 1662.  Boyle's Law states that, for a fixed mass of an ideal gas at constant temperature, the volume is inversely proportional to the pressure.  In this barometer, the fixed mass of gas is above the blue fluid in the glass vessel on the left side of the device.  The glass tube that is exiting from the bottom of the vessel is open to atmospheric pressure.  As the atmospheric pressure varies, the volume of the fixed mass in the vessel changes resulting in a varying fluid level in the open tube.  It does not produce numerical data, but the fluid level in the tube moves down for increasing atmospheric pressure and up for decreasing atmospheric pressure.  For $13 plus shipping it was a novel addition to my instrument collection.

The instructions supplied with the storm glass tell you to fill it half way with colored water, using the supplied plastic syringe and flexible plastic tube.  If you use water, you need to add water from time to time to make up for evaporation.  I varied from the instructions by filling it with drug store mineral oil.  Mineral oil has a very low vapor pressure so it doesn't evaporate significantly.  Mineral oil's density is about 85% of that of water.  If you choose to use mineral oil in your storm glass, here are two bits of advice:
  1. Mineral oil is more viscous than water, so you will have a harder time getting it into the storm glass with the syringe and plastic tube.  Be sure to hold the plastic tube onto the syringe nozzle or it will pop off and make a mess.  I took me about an hour to fill the storm glass half way full.
  2. You need to use oil-based food coloring with mineral oil.  The water-based food coloring in most supermarkets won't mix with the mineral oil.​  I found oil-based food coloring on Amazon.com.
After several months use the mineral oil is working fine.  About 2 drops of oil overflowed onto the plate after a short while, but since then nothing.  No sign of food coloring separation.

The instruction sheets supplied with the Ambient Weather storm glass can be downloaded below (4 pages):
ambient_weather_storm_glass_barometer_manual.pdf
File Size: 203 kb
File Type: pdf
Download File
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