The Storm Glass or "Goethe Barometer" is regarded as the oldest barometer in the world. Although Johan Wolfgang von Goethe (1749-1832) is sometimes credited with it's invention (because one was found in his bedroom after his death), there is evidence that similar instruments were used by the Moors during the 8th century. Also called "Thunder Glasses", historians believe the Pilgrim Fathers sailed to America using this rudimentary barometer.
Using the Storm Glass
Each Storm Glass is hand blown and accurately forecasts changes in weather hours in advance. The storm glass should be half filled with water so that the inlet hole is completely covered and approximately 2 cm remains in the spout. Filling the storm glass can be difficult however the best method is to place the spout under a steady but thin stream of water from a tap and allow the water to flow in slowly. By adding simple food colouring, any colour can be added to enhance the instruments appearance. Once filled, the water in the spout will immediately respond to changes in barometric pressure.No adjustments are necessary after the glass has been filled, but some evaporation will take place over time and more water can be added, when necessary.
How it Works
Our atmosphere has "weight". This pressure or weight changes with the high and low pressure systems associated with our weather.
When the storm glass is filled, the air pressure in the main vessel is "trapped" and held constant. Thereafter, relative changes in air pressure are visible in the spout.
The storm glass does not indicate exact barometric pressure in terms of psi, millibars (mb) or Kilopascals (kPa), but it is highly accurate in monitoring changes in air pressure. The instrument is sensitive enough to display changes in air pressure in a three story house, the difference in pressure between the basement and the attic is visible!
Reading the Instrument
Variations in barometric pressure are associated with weather systems and these changes are immediately revealed by the water level in the spout.A low level of liquid in the spout indicates "high pressure" and fair weather can be expected. A high water level is associated with "bad" weather. In cases of severe weather and major storms the water may even run out of the spout!