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What you need to know before you buy a barometer



As a nation, we are obsessed with the weather, from simply discussing it to trying to predict it, and often we use the weather as an ice breaker, ‘is it going to rain today?’ As an area of scientific antiques, barometers are as relevant today as they have always been.

Meteorologists measure air pressure, amongst other things, to predict what the weather is going to be like – rising or high air pressure indicates fine weather, while falling air pressure will mean more chance of dull, wet or windy weather. The scientific instrument used to measure air pressure is the barometer. Our guide to everything you need to know before buying an antique barometer will explain what they are, how they work and the types available for collectors to buy, as well as the pitfalls to look out for before purchasing an antique barometer.

The history of the barometer

It is generally accepted that Evangelista Torricelli invented the barometer in the mid-17th century. A student of Galileo, Torricelli noticed the correlation between the weather conditions and the change in the level of mercury in an inverted tube. While this did not allow for accurate weather prediction, it did give some indication of what the climate was going to be.

Types of barometer

The design of the barometer has developed to take into factors such as portability, scale and accuracy and today there are two main types of barometer.

Mercury or Cistern barometers – a mercury barometer is the type we think of when considering a barometer and the type originally invented by Torricelli; it consists of a graduated glass tube with one sealed end at the top and an open end which sits in a cup of mercury. The cup containing the mercury is called a cistern.

Aneroid barometers – these do not contain fluid and were first produced in around 1840 by French scientist, Lucien Vidie. Vidie replaced Torricelli’s tube with a metal vacuum disc which rendered the barometer less accurate but much more portable. The aneroid barometer was able to be used outdoors by engineers and scientists and they could be used at sea.

How do barometers work?

A mercury or Torricellian barometer features a glass container filled with mercury. Simply put, at sea level, as air temperature rises, there is an increase in pressure within the container, which causes the mercury level to rise. Conversely, a drop in air temperature will decrease the pressure within the tube and the mercury level will fall. A change in altitude will affect the working of a mercury barometer.

An aneroid barometer features a small, copper alloy box known as an aneroid capsule. Inside the tightly sealed box is a series of springs and levers which will expand or contract with changes in the atmospheric pressure within the box.

While both types of barometer work on the same principle, the mercury barometer is simpler and more accurate. An aneroid barometer can register minute changes in pressure but has a highly complex mechanism.

Styles of mercury barometer

Mural or ‘stick’ barometers were first produced by clockmakers in the late 17th century. Early pieces feature walnut veneers but by the mid-18th century, many were made from mahogany. By the early-19th century, the architectural topped stick barometer was popular and by the mid-19th century oak had overtaken mahogany as the preferred material for the stick barometer. 

By 1665, the wheel barometer, sometimes referred to as ‘banjo’ barometer, had been created by Robert Hooke, an English physicist. The wheel barometer featured the addition of a dial assembly and a circular scale to the stick barometer.

What to look for when buying an antique barometer

A top-quality barometer, in original condition and with a maker’s signature is rare, and when they do come on the market, they are expensive; a Daniel Quare (the inventor of the portable barometer) dating from the Queen Anne period, sold for £40,000 in 2013. Older examples which have survived the passing of time will probably have undergone some restoration and may have had parts such as tubes replaced. This is not unexpected and as long as the buyer is made aware, the barometer will be true and honest. When the restoration of a piece is extensive and unsympathetic however, the barometer may retain its aesthetic appeal but will lose its authenticity and therefore potential value. Similarly, an investment buyer should also be wary of any antique barometer that may have been put together with miscellaneous parts from other pieces.

Whether you are an avid antique collector or you are looking for an antique barometer as a focal point for a room in your home, a sound piece of advice is to buy the best quality you can afford. With current prices for a working antique barometer starting at around £100, this is an accessible area of collectables. When looking for an antique barometer, the collector can choose from the specialist dealer, an auction house or an antiques centre. Auction houses will add a buyer’s premium on to the final hammer price which varies from auction house to auction house; this can be around 20% and VAT is then levied on the premium. It is also always preferable to view antique barometers in person, rather than bidding blind on the basis of an online catalogue. Buying from a Hemswell specialist dealer means you will have access to good advice and you can be reassured that any buyer’s inexperience will not be taken advantage of. Many of our dealers are members of associations such as LAPADA (London and Provincial Antique Dealers’ Association) or BADA (British Antique Dealers’ Association) and all of them are passionate about their pieces.

In these challenging times, when we are currently unable to welcome visitors to our centres, we are happy to make a short video of items you may have seen online and which interest you. The video can be emailed to you or sent via Whatsapp, allowing you to view the item in closer detail. For further details, please contact us by email.


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