The Fortin barometer measures barometric pressure using mercury in a glass tube. It should be calibrated and kept in a stable environment. The mercury can be toxic, and the barometer may need restoration if it is an antique.
Barometric pressure, a measure of the force of the air, is often used in weather forecasting. It is usually measured with a Fortin barometer, in which mercury is encased in glass and travels up and down a metal tube in response to changes in air pressure. A scale helps match mercury levels to barometric pressure at the time of reading. The Fortin barometer is generally used in weather stations as well as laboratories and schools. In 2007, the major manufacturer of the barometer stopped production because the mercury can be harmful to the skin and generally toxic to humans.
A Fortin barometer typically has a screw that allows you to adjust the mercury level. Accurate measurement of the Fortin barometer is often only possible when it has been calibrated at known pressure levels. Measurements should generally be made at the same temperature. Hotter or colder conditions can distort readings, as mercury responds to these changes and to pressure.
The location of the barometer should be out of direct sunlight and should not fluctuate much in temperature. Corrosive substances stored nearby may damage the device, so they must be kept away from the barometer. A heavily trafficked room or area where there is vibration is also generally not suitable for placing the tool. It is often best to hang it at a height where the scale can be read.
Setting the barometer generally requires some attention. It is usually recommended to slowly move the device to an upright position when unpacking and hanging on a wall. The air in the tube can cause damage and affect the accuracy of the mercury. Adjustments made with the screw usually have to be done slowly also due to any air trapped in the tube. When set up correctly, a Fortin barometer is usually very accurate.
The vacuum of an old Fortin barometer is often compromised and antique instruments often need to be taken apart for restoration. Sometimes there is a removable tank, which holds the mercury. If necessary, the liquid metal can be removed with a syringe and stored in a jar while the inside of the barometer is properly cleaned. A pump can be used to seal the tube once the mercury has been reintroduced. Similar procedures can be performed when servicing the barometer or in cases where it is necessary to return it to the manufacturer.
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