Replacing mercury with a metal slug - time keeping effect?

Discussion in 'Clock Repair' started by TJ Cornish, Sep 13, 2018.

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  1. TJ Cornish

    TJ Cornish Registered User
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    I just purchased a significant clock with a mercury pendulum that came with maybe 15lbs of 125-year-old mercury. As I have smallish children and the clock is in a carpeted area as well as the fact that spilling more than 1lb of mercury requires a mandatory notification to the EPA and probably lots of $$$$$ to clean up, I think it's prudent that I take the mercury out of service.

    I have heard of people replacing the mercury with a steel slug. The mass of mercury is 13.5 g/cm^3 and the mass of iron/steel is just over half that - around 8 g/cm^3. Will this have a significant effect on the rate of the clock - that is will it require the pendulum being lowered farther than it can likely go or is the mercury centered over the effective pendulum length such that weight is less of a factor?

    Tungsten carbide is 15 g/cm^3 so I can go that route if I need to, but it's more costly and less available.

    Thanks!

    P.S. - a related question - has anyone attempted to permanently seal the mercury in something more robust than open glass jars - acrylic maybe? It's a shame to have to disable such a cool aspect of the clock. If there was a way to significantly reduce the likelihood of exposure in the event of a suspension spring break or other issue, it would be great to be able to still use the mercury. I don't think I'm comfortable with just sealing the existing glass jars with something like silicone - the jars themselves could crack.
     
  2. bruce linde

    bruce linde Technical Admin
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    i would lose the children before the mercury pendulum? :cool:

    seriously... i assume the pendulum is behind a door with glass in it? you could line the inside bottom of the clock with a plastic tray to catch any mercury should the kids somehow put a ball through the glass door and break one (or more) of the vials containing mercury. from what i recall it's not spilled mercury that's the problem, it's fumes.

    can't imagine the center of mass will change that much, but if the movement is comfortable with the heavier pendulum it should be more accurate.

    it's a significant and no doubt gorgeous clock.... stuff happens, but are you sure it wouldn't be ok to leave it as is?

    and... can we see photos so we can respond with appropriate jealousy?
     
  3. novicetimekeeper

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    Mercury fumes are dangerous, but you would have to get the central heating up very high to suffer from them, the age is not an issue.

    The way the EPA is going they will soon be relaxing that rule too so you probably don't need to worry.
     
  4. R. Croswell

    R. Croswell Registered User

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    The kids need to keep their distance from daddy's clock. The catch pan in the bottom of the clock is a good idea. If the mercury is in glass cylinders with cork gaskets and metal ends I would have some concern with 125 year old gaskets. I would still consider keeping it as it is.

    R C
     
  5. TJ Cornish

    TJ Cornish Registered User
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    The clock is significantly quieter and more reliable than my children. There are moments it has been tempting. :) My kids are wonderful (two boys 9 and 7) and one of them has even caught the clock bug. The boys share a bedroom that has about 25 clocks on the wall.

    I'm going to explore the plastic tray idea. I was thinking of caulking around the bottom of the case, but a tray is better. I should be able to make something out of polycarbonate that wouldn't shatter like acrylic might if the suspension spring broke and the pointy bottom of the pendulum hit the tray hard. I may see if I can glue in some polyethylene closed-cell foam to the tray that would increase the chances that the pendulum would stick in the foam and remain more upright if the suspension spring broke. That would reduce clock damage and significantly reduce the amount of mercury that would potentially splash out of the pendulum.
    I'm waffling. The internet is split halfway between "Mercury isn't dangerous - I routinely broke mercury thermometers in my hot chocolate and drank the whole thing down glass shards and all and I'm totally fine." and "Mercury!? Don't you know that a single atom will destroy the whole city!?!?!?" Since the mercury level hasn't changed in 125 years it seems unlikely to me that the vapor issue is significant short of a house fire boiling the whole thing. I'm more concerned about the spill potential. Perhaps the above modifications are enough.
    I'll share the pendulum, but for now I'm going to keep the clock private. It's a Waterbury and it's beautiful. If you're ever in the St. Paul/Minneapolis area, you can come over for a visit.
    pendulum.JPG
     
  6. TJ Cornish

    TJ Cornish Registered User
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    Lol. Herein lies the rub - having reasonable rules and wisdom and discernment to apply them has never been a strong suit of humanity in general, and government bodies in particular. I like the environment and would like a clean planet, but I don't want the gov't coming and bulldozing the house for a non-material issue.
     
  7. TJ Cornish

    TJ Cornish Registered User
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    Can you elaborate on "cork gaskets and metal ends"? This clock has glass jars with solid glass bottoms but open tops. The brass cap covers the jars but there is no gasket at the top. Are you saying that some pendulums have mercury sleeves with no bottom that is plugged by cork or are you saying that I should explore sealing the top of the jars? If the latter, any recommendations? I don't want to just slob silicone around the top of the jars sealing to the brass cap - the pendulum is difficult to mount and unmount with the jars in place, so being able to remove them is really nice.
     
  8. novicetimekeeper

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    there was a move a few years ago in the EU to ban mercury from the home and introduce stringent controls on business, to be fair it was probably UK civil servants doing their usual think of taking a perfectly reasonable EU proposal and turning it into a nightmare of red tape. However at the time the antiques trade here was in rather better health and managed to persuade them that mercury barometers were rather good for business.

    You are not allowed to send mercury through the post here, but at least we kept our barometers.
     
  9. Uhralt

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    Rather than a plastic tray I would suggest a metal container, maybe a bowl or an old cooking pot for more stability. Just make sure that it isn't made from aluminum because mercury will quickly "eat" the aluminum by forming an amalgam, creating holes. The foam sounds like a good idea.

    Uhralt
     
  10. TJ Cornish

    TJ Cornish Registered User
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    I appreciate the thoughts. What's your concern about plastic - specifically polycarbonate? The advantage I can see is that I can fabricate it myself to the exact dimensions of the clock bottom and even caulk the sides of the pan to the sides of the clock, which would catch a good chunk of the mercury that splashed on the sides of the clock case and funnel it into the pan.
     
  11. Uhralt

    Uhralt Registered User
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    I have no concerns with the compatibility of the polycarbonate but maybe with the mechanical stability. It might get punctured at the bottom by the tip of the heavy pendulum in case it crashes down. However, I also see the advantages of your approach. Maybe you can simulate the impact with something about 15 pounds heavy and having a similar tip? If it doesn't penetrate the foam you should be fine.

    Uhralt
     
  12. TJ Cornish

    TJ Cornish Registered User
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    Polycarbonate plastic is incredibly impact resistant and is used in some bullet-proof applications. Here's a video that demonstrates a 6lb weight dropped from 21' (2.7kg dropped from 6.5m) onto a 1/4" piece of polycarbonate. It will have no problem handling a 20lb pendulum dropped 6" even with a pointy end. The foam will slow the impact slightly as well. For extra paranoia, I could put a second bottom layer on.
     
  13. Uhralt

    Uhralt Registered User
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    Looks good! I wasn't aware of the mechanical properties of polycarbonate, more thinking about something like PVC.

    uhralt
     
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  14. shutterbug

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    My pendulum has a thin cork seal at the tops of the vials. Looks like a cork was fitted into the vials, marked, and then sliced to reduce the size.
     
  15. bytes2doc

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    The other issue with a change in material would be accuracy of the clock.

    The mercury was used as part of compensation system. For example, when the temperature increased, the rod would expand, making the pendulum longer. However, at the same time the mercury would also expand, but in the opposite direction, negating the effect.

    I think it would be more important to find a material with similar expansion properties as mercury more than a similar weight, but I'm no expert and my physicis days are many decades behind me.
     
  16. paradise

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    I have a ST tower clock with a setup at the top of the pendulum which does not touch the pendulum but if the suspension spring should break it would not allow the pendulum to fall any more than 1/8 to 1/4 inch stopping its fall, no damage done. I have a few clocks, not tower clocks, with mercury jar pendulum and have rigged up something similar for them and feel very comfortable with their safety. Perhaps you could do something like that thereby maintaining use of the original mercury pendulum which I don't believe is original to that clock but looks great...….Thanks....Paradiseclocks.
     
  17. R. Croswell

    R. Croswell Registered User

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    Of course if the clock is kept in a climate controlled environment with little temperature change the compensating properties of mercury are much less important.

    RC
     
  18. bruce linde

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    what a great idea... i was just setting up a new howard-style banjo clock and thinking i would do a similar thing with the heavier-than-usual weight... i.e., rig an emergency stop harness of some sort to catch the weight should the weight cord somehow break or come loose. veeerrry interesting.
     
  19. Tim Orr

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    Good evening, Mr. Cornish!

    Interestingly, there was a discussion of a similar issue involving a clock in an office building. This was on the Clockslist forum. While some respondents were adamantly against removing the mercury and altering the horological heritage of the clock, there were some interesting solutions proposed, perhaps similar to the tungsten carbide one you mentioned in your first post. A mixture of tungsten and silver powders was mentioned, among other ideas.

    Temperature compensation would probably be adversely affected, but the truth is that most homes and offices have much tighter temperature control than when these clocks were originally made, and you might not see any great variation.

    Best regards!

    Tim Orr
     
  20. bruce linde

    bruce linde Technical Admin
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    great answers, but... mercury pendulums are totally brilliant.

    maybe i'm just jealous because the only one i have is a mini, in a french crystal regulator, but even if you're not really taking advantage of the temperature compensation, it's still there...
     
  21. TJ Cornish

    TJ Cornish Registered User
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    I thought of something like a safety harness, but I don’t know how you could set it up without it touching the pendulum in normal operation. Do you have a picture of your setup?

    My pendulum is absolutely original to this clock.
     
  22. TJ Cornish

    TJ Cornish Registered User
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    Do you by chance have a link to that other discussion?

    i think this is the crux of the issue. I don’t think there’s any other mechanism to keep the compensating function of mercury with another material - there’s just nothing out there that’s close in both thermal expansion and mass (here’s a helpful table of thermal expansion that shows mercury vs other materials: Thermal expansion - Wikipedia). Interestingly water might be about the second best option (which is probably not practical). But, as you point out, in a home that varies in temperature less than 10 degrees from summer to winter and the fact that I’m not using this clock to time train departures or something life-threatening, it’s hard to argue for the necessity of compensation.

    It’s one of those funny risk/reward dilemmas - in an absolute sense, I’m far more likely to be bodily harmed by the cumulative exposure to French fries than by mercury. I can significantly reduce the likelihood of a significant spill by anchoring the clock to the wall (done), sealing the jars somewhat, building a catch pan in the bottom of the clock, and possibly a safety harness for the pendulum. But, if there is a significant spill, I’m thoroughly buggered. Carpet goes for sure, and maybe much more, not to mention the cleanup costs. I met someone who had this happen - they had a wall regulator with a mercury pendulum that fell off the wall. I wish I would have asked them more questions.

    If I take the mercury out of the clock and keep it (in a safer place than the middle of my house), I can return the clock to original condition easily, and this is arguably better from an originality standpoint than a catch pan or a pendulum safety mechanism.

    One other possibility is removing the mercury and replacing it with something - either steel or tungsten carbide in the jars, and making a new pendulum rod out of Invar. When I got the clock, I disassembled the pendulum because I wanted to assure myself how much travel I had with the regulating nut before the jar apparatus falls off the bottom of the rod, so I know it’s fairly simple - it has a flat machined at one end with a pin and screw hole for attaching to the suspension, and simple threads at the bottom. I think this has the best chance of regaining some compensation performance without the hazmat risk.

    Thanks for the thoughts. I’m still waffling. :(
     
  23. R. Croswell

    R. Croswell Registered User

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    Risk management is almost always a compromise. I would suggest that there may be a greater risk of a mercury spill during your attempt to disassemble the pendulum and remove the mercury than if you just leave it alone. Once removed from the pendulum secure storage is another issue.

    So the kid sees it and says to himself what's that shinny stuff in the jar on the top shelf, I'll have a closer look. Then oops! dropped it, that was a lot heavier than I expected. The jar busted but wow, look at all the little shinny beads on the floor.

    Of course if you are unfortunate enough to ever have a fire all that mercury will turn to mercury vapor........good luck.

    RC
     
  24. Willie X

    Willie X Registered User

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    I agree with RC. Like what do you plan on doing with the mercury when you pour it out of the vials?

    Aluminum foil and #7 1/2 lead shot make a reasonable (and easy) replacement. Willie X
     
  25. Tim Orr

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    Good afternoon, Mr. Cornish!

    The discussion was on the Clocks list. You can Google "Yahoo Clocks List," and then, once you're there, punch in "Mercury" to see the posts. There's probably also a way to extract all the related ones from the list, but I don't get into it enough for that.

    Here's one that seems relevant: Yahoo! Groups

    Good luck and best regards!

    Tim Orr
     
  26. RJSoftware

    RJSoftware Registered User

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    It's not the central heat it's the vacuum cleaner. Mercury breaks up into tiny microscopic beads and if the filter fails to stop them they burn up in the heat from the motor.

    Not worth it. It's like leaving a deadly keepsake for your descendants.

     
  27. novicetimekeeper

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    This seems rather unlikely, unless you are talking about after a spill, there is no way microbeads of mercury will be coming out the top of the pendulum tubes.

    We are looking to get our first mercury barometer soon, looking forward to it.
     
  28. John MacArthur

    John MacArthur Registered User
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    The standard setup is to mount a crossbar near the top of the pendulum rod, and a couple of strong pins protruding from the back of the case just under the crossbar. If the suspension breaks, the pendulum drops very little, but is never in actual contact with the safety pins.
    Johnny
     
  29. paradise

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    I don't have a picture so I will try to describe it, your imagination will be helpful. On the ST there are two solid metal oval shaped rings about 1/2 inch wide and 3.4 inch long on a bracket that is attached to the frame, which in your case would be the clock case or the clock rear plate up at the top of the pendulum. the rings are situated adjacent to and close to the pendulum on each side but still allowing it to swing unimpeded. There is a brass rod going through the pendulum rod up near the top long enough for it to go through the oval holes with an inch or so of overhang. The rod is located such that the motion of the pendulum will not be enough to touch the rings unless the suspension spring breaks in which case the overhang will be stopped being caught by the rings.
    This is on a tower clock so everything on yours will have to be a little modified and scaled down and for my regulators I made a strap for the rod because the pendulum for the tower clock is a thick piece of wood not a 1/4 inch rod. Im sure if I managed to convey the idea properly and you understood what I wrote you should be able to rig up something. Care must be paid to not allowed whatever you make be high up on the pendulum very close to the spring so it would not effect the rate and will also allow only a very short fall before being stopped so as not to cause any movement of mercury of caps...……..Paradise
     
  30. kinsler33

    kinsler33 Registered User

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    If anyone ever died from mercury that drained from a thermometer, barometer, or pendulum in their home I have yet to hear of it. Almost all mercury poisoning is due to mercuric compounds, like the ones they used to make felt (hence the Mad Hatter) or the stuff those Japanese fish were full of in the Minimata incident. Metallic mercury is actually pretty stable and doesn't evaporate readily at atmospheric pressure and room temperatures.

    I'd leave the clock alone.

    M Kinsler
     
  31. Willie X

    Willie X Registered User

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    Me too,

    If it ain't broke ...........

    Willie X
     
  32. kinsler33

    kinsler33 Registered User

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    And if you don't tell anyone that the pendulum has mercury in it, they'll never figure it out. That's because nobody under the age of maybe 35 has ever seen liquid mercury in use--say, in a thermometer or a mercury switch, much less a pendulum. Your average citizen thinks that mercury is that red stuff you see in a thermometer.

    M Kinsler
     
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  33. TJ Cornish

    TJ Cornish Registered User
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    I appreciate all the thoughts and perspectives, as well as the descriptions of methods to arrest the pendulum from falling. I'm going to sleep on this for a while before making a decision, but at the moment I'm leaning to some kind of fall arrest mechanism.

    Once again, my concern isn't whatever miniscule amount of evaporation may happen with the mercury inside the clock - I'm convinced that's a non-existent health risk; my fear is the pendulum spilling and pouring 15lbs of mercury everywhere, and what the local hazmat folks might determine the necessary remediation to be in that situation (gut/bulldoze the house, etc.). If I can keep the mercury in the pendulum, I'll be fine.
     
  34. RJSoftware

    RJSoftware Registered User

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    Consider the welfare of descendants. We can't predict the future but we acknowledge the past. For me is definitely no. When I was young we use to break the glass vials of thermostats. I remember carrying some in my shirt pocket, oblivious. Also remember tossing it on concrete floor of utility room. Why not, I was a kid, it was fun to watch it splatter. My Dad should of said something but maybe he didn't know either. He may have said something, but I was a kid. So no matter what you do short of getting rid of it, it's still poison.
     
  35. TJ Cornish

    TJ Cornish Registered User
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    RJ, your point is reasonable and I appreciate your thoughts. Life is full of hazards, and I'm sure all of us have moments we can look back on and say "But by the grace of God..." That being said, I think it's wise to try to look at risk in perspective, and in my opinion, the word "poison" maybe a bit strong. Many things in the home are hazardous - many people are seriously injured by mixing cleaning supplies - ammonia + bleach for example. The vast majority of us have explosive gas piped into our homes for heating and cooking, and the events in Boston over the weekend illustrate that particular danger. In all of the above examples, we have for the most part accepted that the usefulness of the hazard outweighs the risk, though tragedies do happen. There have been a couple cases of serious injury or death by mercury poisoning, but those are pretty rare and extreme events - e.g. intentionally boiling the mercury out of amalgams to recover the silver. I think the data will reveal that many more people (especially children) die if they try to climb on a piece of furniture - tall clocks being great examples of this - and pulling the item down on themselves.

    I was swayed by earlier posts about storing the mercury outside the clock - on one hand, that removes the hazard from our primary living area to the garage, but on the other hand, it is possible that it could fall off a shelf, be played with by folks who don't know what it is, etc. I think it's reasonable to argue that the mercury is safer inside the clock since spillage would be noticed immediately and action could be taken, rather than the unnoticed spill in the garage for a long period of time.

    It's a fair question to ask whether the risk is worth it at all - most folks agree that having heated homes and relatively germ-free living spaces are fairly high up on the list and worth some risk, and it may be hard to put having a super cool clock at that same level. That said, a lot of folks have motorcycles, go mountain climbing, go camping in bear country, go sky diving, etc. All of those hobbies have a greater mortality rate than clock collecting, mercury or no. Probably the greatest mortality rate in the clock world is spousal reaction to one-too-many clocks. :)

    I haven't made up my mind yet and I do appreciate your and everyone else's perspectives.
     
  36. kinsler33

    kinsler33 Registered User

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    If your house burns down it's rather unlikely that anyone is going to notice the fatal globules (they aren't fatal) in the ashes. Nobody but you (and us) would know that there was mercury in your clock pendulum anyway, and if nothing really odd happens the f. globules will sit in the ground in liquid form forever and won't bother anyone.

    It's worth noting that coal-fired electric power plants add some number of tons of mercury to the atmosphere and thence to the earth every month. I'd heartily suggest that you simply leave the clock alone unless you plan to publicize its existence to the World Council of Exceedingly Unlikely Hazards to Children.

    M Kinsler

    Oh: our local Decorative Arts Center of Ohio, which has a huge old mansion of nifty stuff including a reproducer piano, has a mantel clock--somewhere between French and British, from the looks of the thing--and they always tell everyone that the pendulum contains mercury, and so the clock is all dangerous and everything. Just to make sure, I had another look, and what it has is a gridiron pendulum, with the alternating iron and brass rods. I told them that the pendulum did not and never had any mercury in it, but it's not clear that they believe me.
     
  37. TJ Cornish

    TJ Cornish Registered User
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    Thanks for the thoughts. :)

    RE Gridions - I own one gridiron pendulum clock - a Gilbert No 20 jeweler's regulator. This has the alternating iron and brass rods and looks beautiful...………...but if you look closely at the pendulum, all of the rods are pinned at the top of the pendulum, and only the center rod actually connects to the bob. Not much compensation happening there. :rolleyes: "Fins on a Cadillac" apparently was alive and well long before Cadillacs had them. I looked at a friend's jeweler's regulator (Waterbury 65 I believe) with gridion, and it's the same setup as mine - looks pretty, but not much time keeping advantage.
     
  38. Old Rivers

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    :chuckling::chuckling::)

    Mr. Kinsler,

    "Fatal globules" - love it!
     
  39. kinsler33

    kinsler33 Registered User

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    I have for many years hoped that I would someday be able to convince people that it's worth learning how the man-made world works. Like, where your water comes from, what concrete is, why you owe your life to the guys who maintain sanitary sewers and to building inspectors, what makes a car move, and an airplane fly, and all the rest.

    I gave seminars for science teachers who'd been teaching from canned curricula that riddled with errors, proposed and occasionally taught college courses on the subject, screamed at the state board of education, who couldn't decide if I was trying to revive shop courses (heaven forbid) or teach engineering in high school, and even wrote out a curriculum for general science--that is, the science courses that the unenthusiastic kids have to take. Nothing much has worked, and for my trouble I've seen pseudoscience--anti-gravity, free energy, and all that--grow and prosper.

    Thus we have science museums (e.g., the one we have in Columbus, Ohio) who think that mercury is the red liquid found in thermometers and that asbestos is fatal if touched. Thus the only mercury pendulum I'd ever worry about is one that people know about.

    Mark Kinsler

    don't lots of pendulums contain lead?
     
  40. Time After Time

    Time After Time Registered User
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    Unless the house explodes and the clock gets incinerated, lead won't escape containment.
    If one wants to keep a mercury pendulum in its original form, fine and good but respect the potential health hazard.
    I've had customers ship French Crystal Regulators to me with mercury pendulums. In one instance the guy's packing was pretty "lax" and he gave no warning. I really didn't appreciate the potential mercury spill in my shop. Fortunately, I didn't need to clean one up.
     
  41. RJSoftware

    RJSoftware Registered User

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    Mercury is like shiny magic play stuff. So cool to watch the beads join in one glob. I use to make them join rolling the little blobs I scattered on the concrete floor. The ones I could find. No joke. When your time comes someone will get the clock. Given enough time everything breaks, especially suspension.

    So bang the pendulum drops. There's your great grand son. That catch tray is long gone, why was that there in the first place..? Mercury spilling out running everywhere. Look at this cool stuff. Why do infants put things in their mouths anyway?
     
  42. Jim DuBois

    Jim DuBois Registered User
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    As to one of the questions posed above, yes, if you replace the mercury with a metal slug, timekeeping will be affected. How much sort of depends on the range and duration of temperature changes in the clocks location. As to the danger of mercury, it is extremely low and these clocks have often been around for 150 years or more. And they haven't killed anyone. For that matter when is the last time any of us has read, seen, or been aware of anyone suffering from mercury poisoning? I suspect a seafood diet is more likely to get any of us than our astro regulator in the front hall...and what was that silver amalgam that dentists used to cram in our teeth? " Approximately half of a dental amalgam filling is liquid mercury and the other half is a powdered alloy of silver, tin, and copper. Mercury is used to bind the alloy particles together into a..."
     
  43. R. Croswell

    R. Croswell Registered User

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    The greater risk from mercury is exposure to very very small amounts over a long period of time.

    RC
     
  44. novicetimekeeper

    novicetimekeeper Registered User
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    the only risk from mercury is its compounds. Elemental mercury is not a problem. I know somebody who injected it in his arm to commit suicide. It didn't do his arm much good but he is still about.

    However everybody does their own risk assessments on what they do in life, we should leave you to do your own.
     
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  45. Time After Time

    Time After Time Registered User
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    There's no appreciable free mercury in a silver amalgam. It reacts (very readily) with the silver, tin and copper alloy to form the "amalgam" alloy. Proper placement required the intense compression/compaction of the triturated material to so that the mercury rich layer escaping to the top of mass could be carved off leaving behind a restoration with the least amount of mercury possible. Even so, dental amalgam was generally not recommended for young patients which kind of speaks to RJ's point. Other types of restorative methods or materials were generally preferred and recommended for them instead.

    These days, one often has to look for dental practices still offering silver amalgam restorations. I know of one locally who absolutely refuses to place them.

    If you want to keep a large vial of mercury swinging around inside of a clock, be aware of it and respect the fact that it's a potential health hazard. If not a hazard to you, possibly to young children with developing nervous systems.

    No doubt some of us still inhale smoke from burning tobacco leaves just for kicks and giggles. I doubt anyone would blow secondhand smoke into the face of a grandchild bouncing on their lap.
     
  46. R. Croswell

    R. Croswell Registered User

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    My dentist still uses dental amalgam. Had a filling done last month with that stuff. He claims it is stronger than the new stuff.

    I recall reading about a mercury spill a few years ago, I believe it was in a school. After the cleanup I believed they used some sort of sensitive instrument to sample the air quality to confirm if the cleanup was complete. I haven't been able to find much information but I believe liquid mercury may have a very very small vapor pressure t room temperature. It will oxidize if left exposed to the air. In old times I have read where doctors would give mercury to patients as medicine. Not sure how civilization ever survived ancient medical practice.

    RC
     
  47. Uhralt

    Uhralt Registered User
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    I remember reading that liquid mercury was swallowed to treat constipation.

    Uhralt
     
  48. Time After Time

    Time After Time Registered User
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    Well, as I mentioned, one practice down the street absolutely refuses to use the stuff. They prefer to use their fancy (expensive) CAD/CAM equipment instead. The practice I go to will place them but only upon request. Silver Amalgam has been used for quite some time as a relatively inexpensive, direct restorative material. It was (and may still be) the standard against which other restorative materials were compared. Whether or not there have been deleterious effects on folks constantly chewing on these types of "fillings" depends upon who you read. Most recognized authoritative sources will say there's no evidence of mercury poisoning. When I practiced, dentists who recommended routine replacement of amalgams with other materials were generally considered to be quacks or crooks. That was my impression anyway. It's also my impression that the Profession is slowly moving away from the use of restorative materials containing Mercury.

    Never heard of Mercury being used as a laxative before. Wonder what people will think of our medical practices a Century from now? Maybe the clock in question will still be ticking away with its Mercury Pendulum.
     
  49. TJ Cornish

    TJ Cornish Registered User
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    #49 TJ Cornish, Sep 18, 2018 at 12:21 PM
    Last edited: Sep 18, 2018 at 12:28 PM
    I appreciate the continued perspectives. I have learned a lot from you all and my own research.

    There's no doubt the mercury is a hazard in certain situations, however many things are more toxic. Touch metallic mercury and you will be fine, though washing your hands is probably a good idea. Touch lye and you will get a heck of a chemical burn. Drink metallic mercury and you might get some small exposure, but mercury is not soluble in stomach acid (HCL), so it comes out the other end intact. Drink ammonia or bleach and you're headed for the hospital or the undertaker (sadly this is a common killer of children who get into the cleaning supply cabinet).

    There's a guy with a YouTube channel - Cody's Lab. He does a lot with mercury, and owns something like 800lbs of the stuff. His credentials are a strong background in chemistry and geology. He has addressed the health effects a couple times, including posting the results of a blood test he took after a significant mercury exposure (sticking his entire arm into a vat of mercury, IIRC) with no elevated levels. He made a video where he describes the process to clean up spilled mercury and addresses a critical comment about his cleanup methods by stating that "
    a can of tuna-fish contains about a micro gram of mercury and if you collected it all into a droplet of mercury it would actually be visible to the naked eye! and I'm sure you feel fine eating cans of tuna every now an then." (the comment is from about a year ago and I'm not sure how to link directly to it, but you can browse through if you want to.

    I tried to do the math on how large a microgram bead of mercury is - the amount in a hypothetical can of tuna. Please feel free to point out any errors in my math, but based on a weight of 13.5g/cubic centimeter, a microgram bead would be about 0.05mm in diameter. This is small, but visible.

    Looking at this another way - the OSHA limit for airborne mercury vapor is 0.1mg/cubic meter of air volume. A 0.1mg bead of mercury is about 0.24mm in diameter. A 3 meter square room with 3 meter ceilings is 27 cubic meters. You could completely vaporize 2.7mg of mercury in this sealed room (about a 0.7mm diameter bead) via any mechanism you choose - vacuum motor, fire, etc., and be in this room 40 hours per week and still not exceed the OSHA limit. Obviously changing out the air in the room drastically reduces the exposure.

    This leaves the question "How fast does mercury actually evaporate, and how does temperature affect this?" I'm quickly getting beyond the point of a reasonable amount of time put into a forum post, and it's been a couple decades since physics or chemistry class, but according to this chart, mercury vapor pressure is very low and doesn't start accelerating until around 150°C. My 125-year-old clock has quite a bit of mercury from a volume standpoint, but in its 125 years of operation, it doesn't seem to have lost much mercury in the pendulum (I believe the oxide layer that forms slows evaporation as well).

    Herein lies the conundrum of mercury. If it evaporates quickly, then it's an urgent problem, but then is actually short-lived, because a high evaporation rate means that after a short period of time, it's gone (venting, etc.). This can happen if the mercury is heated to a couple hundred degrees Celsius, but in any reasonable temperature range fit for human habitation, evaporation is very low, meaning that even though it may hang around for a long time, since it's hard to get it to actually vaporize, the health hazard is modest at best. If I spilled 15lbs of mercury onto my carpet and vacuumed it for long periods of time with no other attempts at cleanup, I suspect that the health hazard is very real, and that would be "not a very good idea"©. As long as the mercury stays inside the clock, I've convinced myself it's not a health hazard. My kids are old enough to understand that they need to be careful around the clock (we've already had that discussion), and if something significant happened, they would tell us right away and we would deal with it. Even in the future when we hopefully get to experience grandchildren, there's simply no way that even an infant could get any measurable dosage from the contained mercury in the clock.

    My concern is about handling spillage. A polycarbonate catch tray in the bottom of the clock significantly increases containment of the mercury that may get out of the pendulum, and a fall-arresting mechanism placed on the pendulum shaft significantly reduces the chance of any mercury escaping the pendulum jars in the event of a suspension spring failure or movement mount failure. I'm going to explore these two options further. For now, the clock is screwed to a stud to eliminate the tipover risk, and I have serviced the movement and inspected the suspension spring. There are no wrinkles or cracks, so I should be safe for a while.

    Thanks for sparking me to do the research - I learned a lot.
     
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  50. kinsler33

    kinsler33 Registered User

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    Our house, on the other hand, came equipped with asbestos-cement siding, since covered with vinyl because it proved impossible to paint the old siding. We just kept quiet about it, and there are lots of other houses nearby with the same siding, installed in 1957, we think.

    There used to be a plastic puzzle for kids consisting of a maze a respectable globule of Hg. I suppose they're not selling these anymore.
     
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