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Rust On Hairspring: Harmful To Leave It?

JuliusSqueezer

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Mar 17, 2021
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I have a pocket watch with a speck (very small, you have to go looking for it under just the right lighting) of rust on the Hairspring.

I have no idea how it got there but I’m assuming it’s been there the whole time I’ve been in possession of the watch (which is running fine, albeit a bit fast) but I’m not 100% sure as I didn’t see it when I did an initial inspection.

Is it harmful to leave it alone and pretend I never saw it?

If it is harmful to leave it, what should be done about it?

Also, what causes rust in watch movements?
If everything is clean and dry at the time of assembly without rust, what is the likelihood of rust forming if carried in the humid summers of SW Ontario in the watch pocket of blue jeans (double humid from perspiration)?

Another watch I have has been growing (for lack of a better term) rust in the screw slots. I’ll remove it by scraping it out, dipping the screw in lighter fluid, drying it up with a blower and a week later it’s back.
Why?
What am I doing wrong?
Is it just the weather conditions (humid summers) of where I live?
 

JuliusSqueezer

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Condensation?
Maybe?
I’m not sure as there have been no sudden temperature shocks to either watch.
I don’t have air conditioning in my home, nor do I work in air conditioned areas.
The shops I’ll visit are 5-10 degrees Celsius cooler than outside (as they are cheap these days) and either watch is in my pocket at body temperature, which is quite a bit higher than the air conditioned areas.

The movement with rusty screws has rust that looks like a brown rust, suggesting that the metal is in decay for no particular reason?
The one with rust on the Hairspring also appears to be brown rust, however, it’s very hard to tell as the lighting has to be just right even to see it.

I don’t understand why this is happening. Either way, I’m not enjoying worrying about the future function of watches I’d like to give to my grandchildren so that they can give them to their grandchildren, should the latter show up at any point and produce the former.
 

gmorse

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Hi JuliusSqueezer,
The movement with rusty screws has rust that looks like a brown rust, suggesting that the metal is in decay for no particular reason?
The one with rust on the Hairspring also appears to be brown rust, however, it’s very hard to tell as the lighting has to be just right even to see it.
Iron oxide, (aka rust), is usually brown, unless there's something else going on as well. The corrosion products from other metals vary in colour, with the other one you're likely to see being the green of copper alloys such as brass. Iron and steel will rust in the presence of water and oxygen, and once it starts, it needs to be neutralised chemically, because if it's just removed physically without remedying the causes, it will return. Phosphoric acid is one of the old treatments, strong tea is another, but now there's Evaporust and electrolysis as well.

Rust on balance springs is a problem, because neutralising it usually results in loss of the bluing, and if left, it will affect the strength of the spring. Replacement is the only option in the end.

Regards,

Graham
 

JuliusSqueezer

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Mar 17, 2021
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Hi JuliusSqueezer,


Iron oxide, (aka rust), is usually brown, unless there's something else going on as well. The corrosion products from other metals vary in colour, with the other one you're likely to see being the green of copper alloys such as brass. Iron and steel will rust in the presence of water and oxygen, and once it starts, it needs to be neutralised chemically, because if it's just removed physically without remedying the causes, it will return. Phosphoric acid is one of the old treatments, strong tea is another, but now there's Evaporust and electrolysis as well.

Rust on balance springs is a problem, because neutralising it usually results in loss of the bluing, and if left, it will affect the strength of the spring. Replacement is the only option in the end.

Regards,

Graham
Thanks Graham.

When you say “replacement is the only option in the end”, how long until “the end” comes and the spring no longer works as intended?

Different factors are at play for each different spring, but is there a general consensus on lifespan post rust?
 

gmorse

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Hi JuliusSqueezer,
...how long until “the end” comes and the spring no longer works as intended?
When the spring loses enough elasticity to prevent it being brought to time, or until it breaks! There's no hard and fast criterion, but these springs can be so thin and fragile that sometimes a tiny spot of rust will be the point at which it breaks. It's really down to how the spring behaves in use.

The strength of a spring is inversely proportional to its effective length, directly proportional to its width and proportional to the cube of its thickness, so a very slight rust pit will have a relatively large effect on its strength at that point.

Regards,

Graham
 
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darrahg

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You need to check the condition of where you are storing your watches and consider using desiccators. Moisture or a substance used for servicing is most likely the cause . Don't forget touching with bare hands however this is usually slower in reaction. I live in a humid area and have had no problems with storage, however, I do use desiccators and usually check them a couple times a year just to be safe about it. I have even stored some of them with desiccators in thick plastic bags when they are not in a controlled environment. Good luck in finding the problem.
 
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JuliusSqueezer

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You need to check the condition of where you are storing your watches and consider using desiccators. Moisture or a substance used for servicing is most likely the cause . Don't forget touching with bare hands however this is usually slower in reaction. I live in a humid area and have had no problems with storage, however, I do use desiccators and usually check them a couple times a year just to be safe about it. I have even stored some of them with desiccators in thick plastic bags when they are not in a controlled environment. Good luck in finding the problem.
I don’t really store the watches. They’re on rotation in my pocket and used as intended. When they’re not in my pocket, they’re on my dresser.

The only substance I’ve used for cleaning is lighter fluid -which contains no water- and I’ve been extremely careful not to go anywhere near the Hairspring without gloves on.
 

gmorse

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Hi JuliusSqueezer,
The only substance I’ve used for cleaning is lighter fluid -which contains no water- and I’ve been extremely careful not to go anywhere near the Hairspring without gloves on.
It could well have started long before you acquired the watch!

Regards,

Graham
 
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klokwiz

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Julius, assuming the rust spot on your balance spring is as small as you describe there is not much to worry about. As Graham says it could have been there a very long time. as long as the spring is not developing rust all over there is not much to do. And the likely hood of it effecting timing is low. the spot is either from s defect in springs original bluing or it got a spittle drop from someone blowing on movement or some such thing.

the other watch screws rust issue will not be solved by cleaning. you need to re-blue the screws. You could try a cold bluing process such as used for spot bluing on gun metal. it is a chemical process vs the heat bluing. bottles of bluing are available from a lot of sources. or you can learn to blue them as they were originally.

joe
 
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JuliusSqueezer

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Julius, assuming the rust spot on your balance spring is as small as you describe there is not much to worry about. As Graham says it could have been there a very long time. as long as the spring is not developing rust all over there is not much to do. And the likely hood of it effecting timing is low. the spot is either from s defect in springs original bluing or it got a spittle drop from someone blowing on movement or some such thing.

the other watch screws rust issue will not be solved by cleaning. you need to re-blue the screws. You could try a cold bluing process such as used for spot bluing on gun metal. it is a chemical process vs the heat bluing. bottles of bluing are available from a lot of sources. or you can learn to blue them as they were originally.

joe
It’s hard to see and quite small.
Here’s a picture:

1631938326236.jpeg

This is literally the best shot I could get without taking the watch apart again.

The other movement with rusty screws is another lower grade Elgin from the 1920s without blued screws.
Would it look weird if I did blue the screws?
 

gmorse

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Hi JuliusSqueezer,
The other movement with rusty screws is another lower grade Elgin from the 1920s without blued screws.
Would it look weird if I did blue the screws?
Well, once you remove the rust you'd need to re-polish the screws before bluing them, so you could just polish and leave it at that. Trying to blue without polishing first won't produce a good blue.

Regards,

Graham
 

klokwiz

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Julius, did not realize the other screws were not blued. It may be easier to locate replacement screws. If it is a twelve size elgin i have lots of parts movements. post a photo of movement with rusty screws.

the balance spring is hard to see in photo is it a strip of rust probably a few milimeters on outer turn? if surface and not perforating the spring not a big deal i would try to lightly rub it off and add a tiny dab of oil to protect it if on outside coil do not get oil on coils as it will effect rate of watch but this is tricky since any bend of spring will effect watch. maybe best left alone.

joe
 

JuliusSqueezer

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Mar 17, 2021
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Julius, did not realize the other screws were not blued. It may be easier to locate replacement screws. If it is a twelve size elgin i have lots of parts movements. post a photo of movement with rusty screws.

the balance spring is hard to see in photo is it a strip of rust probably a few milimeters on outer turn? if surface and not perforating the spring not a big deal i would try to lightly rub it off and add a tiny dab of oil to protect it if on outside coil do not get oil on coils as it will effect rate of watch but this is tricky since any bend of spring will effect watch. maybe best left alone.

joe
Hi Joe,

Sorry for the late reply and thank you for the offer of some parts, but I’ve cleaned and polished the screws from the Elgin movement to see if I can keep it “original”.
Fingers crossed that it worked!

As for the Hairspring, yes, just a dot on the second coil of the spring. I’ve opted to leave it alone and just monitor it for changes in time keeping - so far so good. Excellent, even.
 

DeweyC

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Julius, did not realize the other screws were not blued. It may be easier to locate replacement screws. If it is a twelve size elgin i have lots of parts movements. post a photo of movement with rusty screws.

the balance spring is hard to see in photo is it a strip of rust probably a few milimeters on outer turn? if surface and not perforating the spring not a big deal i would try to lightly rub it off and add a tiny dab of oil to protect it if on outside coil do not get oil on coils as it will effect rate of watch but this is tricky since any bend of spring will effect watch. maybe best left alone.

joe

Just to be technically accurate, the acceptance of rust on a balance spring is completely dependent on your expecations for performance, If you demand factory performance, any rust on a balance spring is cause for replacement.

By definition, oxidation has reduced the spring and thereby made it weaker. This has changed the behavior of the osicillator. The watch cannot perform at factory levels.

It is entirely possible for a 120 year old RR watch to keep time within 5 seconds a day across positions (better than Rolex factory specs), The oft stated expanation that "it is old and cannot be expected to perform as new" is more a refelction of what the watchmaker or owner is willing to do and not a statement of fact.

This is why companies like Hamilton offered balance springs in 6 strengths and ordered by the number of screws on the balance.

Most collectors are not overly concerned about retaining factory performance and focus on aesthetics. So this is a marginal issue for most; but if an owner demands original performance, the spring must be changed and the balance itself tuned to that spring. A laborious process.

Regards,

Dewey
 

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