I'm curious if a watch can eventually, over a period of years, demagnetize itself? Eons ago (8 years at least) I bought a Hamilton Khaki limited edition mechanical watch, but when I got it it ran REALLY fast - like 10 minutes a day. So I never ended up wearing it, and since I didn't want to pay more for servicing the watch than I had paid for it, it's just sat in my watch box. I always thought it might be magnetized since it was so far out of whack, but I didn't ever do anything about correcting it. In the last couple days I decided to see if it still had an issue. I wound and set the watch, and then put my Casio Oceanus radio sync'd watch in next to it to see how well it did. Surprisingly it's actually kept time pretty well. I mean it's off by about 22 seconds (fast) after 24 hours which isn't great, but is a darn sight better than it used to be.

I'm going try wearing it for a day or two to see if there are any wilder swings, or if maybe 8 years in the watch box was enough for it to degauss itself.

 

The time to delve into the gaining problem you described was while it was gaining. A lot of things can contribute to causing a watch to gain. The last one that crossed my bench belongs to a friend who had a problem with the watch gaining. Before he brought it, he told me he wanted me to check it for magnetism. I didn’t. I put it on the timing machine to see it was indeed gaining. Lots. I checked the hairspring to find the outer coil was hung up on the curb pins on the regulator. That was easy to solve, and I remedied that problem as he watched. Back on the timing machine. Better, but still gaining, and showing a pattern I didn’t like. I pulled the balance wheel and found that the second coil of the hairspring was touching the hairspring stud with the wheel and hairspring at rest. That meant that, while the watch was running, the second coil of the hairspring was rubbing on the hairspring stud, half the time, That was a simple adjustment. Put the balance wheel and the cock back in place, and back on the timing machine. Problems solved, a slight adjustment to the regulator, and the watch is within seconds per day. Without going anywhere near the de-magnetizer!

Perhaps the hairspring was hung up on the regulator gate or curb pins, and over time, the problem vanished because of a bump to the watch.

I’m not saying that magnetism is not likely to cause a watch to run erratically. (I get into trouble when I say that!) i’m Saying it is always the last thing I check. I don’t remember the last modern watch to cross my bench that was erratic because it was magnetized.

Can a watch gradually become de-magnetized over time? Read the first sentence in the first paragraph, above.

 

Just de magnetized my Midland. When i got it it ran well over two minutes fast per day. Months later after being run 24/7 it was around one minute fast. I tried the demagnetizer and it immediately went to less than 10 seconds fast per day.
Also my 80's Bulova was on my wrist when I demagnetized the Midland. It had been running a bit more than one minute fast, now its down to around 20 seconds fast per day. I'll try the process on it next to see if it becomes more accurate.

from now on I'll try the demagnetizer first whenever I encounter a watch that runs fast, even a little fast. It certainly doesn't hurt the watch and can settle the question one way or the other very quickly.

With modern mail scanning devices being exposed to a magnetic field is very likely. Also shipping a watch might result in it riding for days in a container that also contains speakers or other hardware with very strong magnets.

PS
A 60's Bulova ladies self winder I got for my sister ran very fast 10 minutes fast per hour. I kept it running 24/7 and after a couple of weeks it settled down to one minute fast per day. I'm fairly sure it was exposed to a strong magnetic field in transit. I'll try the process on it and see if the accuracy improves.

 

Very similar thing happened with my Rolex GMT II 16710 Coke, where the hairspring was hung up, but on the second fix it was a drop of oil on the hairspring that had to be removed.

After that fix (about 2 years after it was serviced by Pieces of Time) I then ran it for 353 days straight, on wrist and winder, and it only lost 48.7 seconds in that almost 1 yr period!

 

Yes after a period of time an object which was magnetized can become demagnetized.

 

Well as I feared it was not so simple. After wearing it from yesterday afternoon till this morning it has now gained about 7 minutes. Just for fun yesterday I tried one of those timegrapher apps that listens to the watch to determine beat error etc. And it was ugly... ranged from -7s to +16.5 minutes depending on position. Basically all over the map, and not even consistent based on position. So it definitely needs to be serviced.

This particular model is the limited edition mechanical that came out at the same time as the Pearl Harbor movie (2004?). The face is loosely based on the Hamilton GCT pocket watch (why???) and was "limited" to 3333 pieces. I got this for a good price, but a service would still be significantly more than what I paid for it, so likely back into the watch box it goes.

 

I’ll say it again. I check for everything else before I put it through the de-magnetizer.

 

I like to say that when you buy a decent but mid-price mechanical watch, at a really low price, that you're really only leasing the watch, and the monthly lease price is the cost of the 5 year service divided by 60.

But if you buy something like a Seiko SKX007, then instead of a service you can just get a new Japanese movement installed every 5-10 years for about $150 (maybe $200) in parts and labor, which might be cheaper in some cases than a COA (clean oil adjust). The problem is that sometimes it's only $50-150 more for a whole new watch, although that's not the case with a Swiss watch or an LE model.

My watchmaker gives me a volume discount, and so it's still affordable to have him do a COA on my cheap watches if one is sentimental (1996 SKX009).