Charles Edwin - antique clocks and barometers


 
How to Move and Handle a Mercury Barometer

Concerned about mercury in your barometer? See

Can Your Antique Mercury Barometer Damage Your Health?


Barometers can be moved around successfully, but care must be taken to prevent (a) air from entering the mercury tube, (b) mercury from being lost, or (c) the rather fragile glass tube from being broken. Charles Edwin Inc. offers these instructions to help you prepare your barometer for a short or long move.

SHORT MOVE. Nearly any barometer can be safely moved for a short distance without special preparation, just by taking the barometer off its hanger, tilting it slightly to make the mercury rise to the top of the glass tube, and carrying it slowly and smoothly to a safe place. Keep it tilted at all times; this will prevent the mercury from surging up and down in the tube and either drawing in a bubble of air, or breaking the end out of the tube. If the barometer is to be stored for a short time, prop it as nearly vertical as possible in a safe corner. Return it to its home on the wall in the same way. Smooth and easy does it. Make no sudden movements.

LONG MOVE. A move to another household is a more serious matter. Probably the best advice is to take the barometer in the car yourself, and don't let the movers touch it. If there's no way to avoid giving the barometer to the movers, prepare it as described below and then supervise while the packers pad a wardrobe box with pillows and pack the barometer in the proper position inside. Surround it with pillows so it can't shift during handling.

There are several types of barometer, and each has to be moved in a slightly different manner to protect it. Links are to pictures in our catalog-- don't forget to come back.


BANJO (DIAL or WHEEL) BAROMETERS

Banjo barometers all have essentially the same form of mercury system. To prepare one for a long-distance move, you'll need two size 00 or 000 corks, which can be found at hobby and hardware stores, and a little masking tape. Take the barometer gently off the wall, turn its back toward you, and set it on an upholstered chair or couch, tilted 45 degrees off of Dial Pluggedvertical.

      • Open the back door. The wood door may bind a bit, so work it open gently and resist the urge to pry it open with a screwdriver.

      • Inside the back is a brass pulley with a string hanging from each side of it. Be very careful to keep these strings from unwinding from the pulley. Cut a one-inch length of masking tape and lay it across the strings, just below the pulley, taping both strings down flat against the inside of the case.

      • Cork the open end of both tubes, with their strings and weights still inside. Keep the barometer tilted at 45 degrees at all times until you hang it on the wall again. Carry it in the car cushioned, plastic bagged, and supported.

      • When you again hang the instrument, just reverse the steps above. First take out the corks, then be careful when you pull off the masking tape below the pulley, to prevent pulling the strings out of their grooves. Tilt the barometer back to vertical and hang it.

STICK BAROMETERS

Stick, or straight-tube barometers are made so that you read the mercury directly from the top of the visible glass tube. They will generally have either of two types of mercury reservoir (cistern) at the bottom of the glass tube: a cylindrical wood cistern with a closing screw, or a glass bulb. To determine which you have, you'll probably have to remove the round wood cistern cover from the bottom of the case. It will either pull straight off forward, being held on by two small brass pins in the wood, or will have to be removed by turning the case around and taking two screws out of the rear. Keep the barometer upright while you do this.

Boxwood Cistern Wood cistern with closing screw. The cylindrical cistern, or reservoir of mercury, is sealed to the bottom end of the glass tube, and also has a leather diaphragm in its base. The closing screw, more properly called the portable screw, is a threaded brass rod that protrudes from the bottom of the barometer. When the screw is turned upward, it compresses the diaphragm and expells some of the air from the cistern.

Take the barometer gently off the wall and tilt it slowly back, to about 45 degrees. The mercury will rise in the glass tube and fill the empty space at the top. With the instrument still tilted, turn the closing screw clockwise until you have pushed the leather diaphragm upward about one-quarter inch.

Don't force the screw, or you may tear the leather out of the cistern. The barometer should now be gently laid flat, and kept horizontal until you are ready to hang it again. When you get the barometer to its new home, hang it on the wall and then open the closing screw as far as it will go.

Note: Ships' barometers work with a wood cistern as above, but the closing screw (on those that have one, they don't all) is not readily visible, being inside the brass cylinder on the bottom of the case. Take the barometer out of its gimbal mount and tilt it gently and very slowly, giving the vacuum space at the top of the tube all the time it needs to fill completely. Ships' barometers should have a glass tube that sharply restricts the movement of the mercury, and it will flow very slowly. (This feature allowed them to be used on ships in rough seas, protecting the fragile glass tube from surging masses of mercury.) Now unscrew the very bottom cap of the brass cylinder, uncovering the knob of the closing screw, and then turn the screw upward against the leather as described above. Again, transport the barometer laying flat. If your ship's barometer doesn't have a closing screw, just let the tube fill completely up at the top and then lay the barometer nearly horizontal, with the top slightly elevated, to transport it.

Bulb Cistern Glass bulb cistern. Stick barometers without a wood cistern and closing screw have a glass tube that is bent in a short "J" shape at the bottom. The short leg of the "J", which is behind the removable wooden cistern cover on the bottom of the case, is topped with a glass bulb about half full of mercury, with an open spout. With the barometer in your hands, held vertical, and the cistern cover off, tilt the barometer back slowly and let the top of the tube fill with mercury. Then cork the open spout so the mercury can't splash out. A size 00 or 000 cork will do, and can be found at hobby shops or hardware stores. If you can't find a suitable cork, plug the open end of the tube with a cotton ball and tape it over very thoroughly. Carry the barometer in the car at a 45 degree tilt only; never lay it flat. It will travel safely if you prop it in the back seat with pillows, and cushion the bottom end against sharp bumps.

Admiral Fitzroy barometers are actually a type of stick barometer, and have large, visible bulb cisterns, behind the front glass, that work as described above. If the barometer was made with a closing device and plug (and by some miracle it is still working) you can get at the lever that works the closer from the back of the case and drive the cork down into the open end of the bulb. Don't use a lot of force. If the tube is open and no closing device is visible, take the bottom wood moulding off of the barometer via the screws up through the bottom side, slide the glass panel down and out of the case, and cork the open end of the tube. Carry the Fitzroy at a 45 degree angle also, no matter what type of closer it has.


ALL-BRASS BAROMETERS such as Fortin laboratory barometers.

There are many variations of these, and some have closing screws either inside or outside their brass cistern assemblies while others have no method for making them portable at all, or a method so obscure that only a specialist can work out how to make it operate. They all seem to have two things in common: (a) their glass mercury tubes are ridiculously fragile, and (b) the cistern closing assembly is better left untouched unless you really know what you are about. The best advice we can give is to just tilt the barometer slowly and gently to 45 degrees and let the top of the tube fill with mercury, then transport the barometer at that angle. Be sure to wrap the barometer in a good, stout plastic bag to contain any possible mercury spills, and cushion it well. The mercury system in these barometers is nearly always sealed against loss, but the glass tubes can break.


THINGS TO REMEMBER ABOUT BAROMETERS

  • Remove any gold or silver jewelry before handling a barometer. Mercury amalgamates with precious metals, and makes permanent, ugly grey stains on them.
  • Transport any barometer in a plastic bag. If you should have a mercury spill, it will be contained safely.
  • Don't let a barometer stay in a closed, hot car too long. The mercury will expand and pop the cork out or squeeze through the leather cistern bottom.
  • If you have to move an open barometer around, move in slow motion. If the mercury surges to the top of the glass tube, the tube may be broken.
  • If there are any small, loose parts, such as the set knob below the dial on a banjo barometer, put the parts in a baggie and rubberband them to the case.
  • Don't forget to insure your barometer along with your other antiques. Most household contents policies offer a fine arts rider at a small extra cost, but may exclude antiques under ordinary coverage. The prices in this catalog may help to determine the replacement cost of a barometer similar to your own.
  • As you may be aware, exposure to large accumulations of mercury vapor over a long period of time can be harmful. The very small amount of mercury in your barometer (usually less than four ounces in a fully-filled banjo and less than six ounces in most sticks) that is exposed to the air in a room with average ventilation carries minimal risk. Do treat even a small spill of mercury with respect, though, and dispose of loose mercury in a tightly sealed container at a disposal site that takes used batteries. Such small quantities of mercury have no commercial value.
  • Remember that the barometric pressure seldom changes more than an inch or so at any time. Dramatic fluctuations only occur with very severe weather, so don't be alarmed if your barometer doesn't seem to move for weeks on end, especially during very hot summer weather.
  • Don't try to take your barometer with you on an airplane, no matter what the seller tells you. All airlines have very stringent regulations about hazardous materials, and mercury is high on their list. If you are caught trying to sneak a barometer aboard a flight, you will at the very least be detained, and at the worst could lose the barometer and/or be heavily fined. Plan ahead and ship the instrument, or better yet buy it from a local specialist.

Charles Probst,
1 August 1996




 



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