There’s not a whole lot of things in watchmaking that can mess ya up, but Radium Watches is definitely one of them.

Most people who have been around vintage watches know the story of the Radium Girls, The advice you typically see on forums is, you’ll be fine, just don’t lick it. So I thought I would approach this important with a lot of science and a little bit of common sense

Luckily for us, there is an in-depth study that specifically looks at the risk factors from watches contaminated with radium paint in all kinds of scenarios.

So give me about ten minutes and I promise you, you will see Radium watches in a whole new lite.

First, let me say that the purpose of this video and article is not to tell you whether or not you should wear or work on watches containing radium. This is purely informational, based on credible, published documents that I will link to in the description.  It’s up to you to decide what your own comfort level is based on this information.

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Radium Timepiece Dose Modeling Report

I became aware of the Radium Timepiece Dose Modeling report about 15 years ago not too long after it was published. 

This is an 86-page technical document that provides radiation Doses to the body from exposure to radium when wearing a watch with radium as well as Dosage when performing watch repair. 

Radium Timepiece Dose Modeling Report
Radium Timepiece Dose Modeling Report

Now you can knock yourself out and read how they calculated all this out but I am just going to look at the summaries. 

Measurement Abbreviations

Before you can fully understand and be able to judge for yourself, the potential risk factors of a watch that you might have, and compare it to the testing results, that the Oak Ridge study did,  you need to understand a couple of key measurements.

The first is μCi. μCi (microcurie) is the amount of radioactive material present in the watch or whatever you are measuring.

And why that’s important because, in the study, the testing models were based on 1 Microcurie of Radium, which you are going to see is not very much.

uSv/h (Microsievert) is a very very small unit of radiation and measures the amount of radiation that would be absorbed by the body per hr. Microsievert is important because it’s one possible reading you get on a Geiger counter and you can convert a microsievert to the next unit called Millirem.

(mrem) Millirem is also a unit of radiation dose measurement and is just a larger unit than Microsievert.  Millirem is important because it’s what all the results of the dosing models in the report are based on and The NRC’s radiation limits are based on MIllirems.

 Now when you look at the maximum limits of radiation, The U.S. Nuclear Regulatory Commission (NRC) has established dose limits for occupational exposure to radiation exposure at 5,000 Millirem (mrem) per year. These are the limits set for people who work in the Nuclear medicine and Nuclear Energy fields. 

NRC Radiation Maximum Dose
NRC Radiation Maximum Dose

The NRC  study also shows that the average yearly exposure to radium is about 620 millirem from all sources including food, the environment, and products that use radiation, like smoke detectors and xrays.

Natural Exposure Amounts to Radium
Natural Exposure Amounts to Radium

So here is where you have to decide your comfort level. On one hand, you are going to get 600 millirems just living on the earth, and on the other hand, you have this government agency, whose sole purpose is nuclear energy, saying that 5000 millirems per year of whole body exposure is still considered safe. 

So the question you need to answer is how close to that 5000 mrem a year are you willing to get?

Effective Dosage When Handling Radium Watches

Dose to self from wearing a timepiece 

When we are talking about exposure from a watch that is worn, there are two types of exposure you have to consider.

The first is Shallow Dose, which is shallow tissue exposure where the watch is worn. The second factor is the Effective Dose, which is the radioactive exposure to your internal organs and is the one I will be focusing on because it’s this type of exposure that the NRC’s occupational maximum of 5000 millirems a year is based on.

In the Radium Timepiece report, the effective dose when wearing a wristwatch with 1 Microcurie of Radium is 61 millirems per year. 

Amount of Radium exposure when wearing a wristwatch
Amount of Radium exposure when wearing a wristwatch

Pocket watches on the other hand are a whole different story because they typically are worn much closer to internal organs. 

In this model, we can see that a pocket watch has an effective dose rate of 480 Millirems per year.  

Pocket Watch Radium Dose Result
Pocket Watch Radium Dose Result

There are also 2 important variables calculated in this model. The first is that this particular model is based on wearing the watch for 16 hours a day, every day of the year.

But, these numbers are based on there only being 1 microcurie of radium present which is not very much as you will see in a minute.

Dose due to amateur repair activities 

So what about opening up a watch and working on it? 

Well, they also did a model for that as well. When working on a watch with 1 microcurie of radium, the effective dose to your body is 15 Millirems per year for 1 watch. 

Amateur Radium watch Repair dose results
Amateur Radium watch Repair dose results

This takes into account external exposure, inhalation, and ingestion of some paint particles, as well as inhalation of radon gas.

What’s interesting about their modeling calculations, is they are assuming that the watch will be handled for about 25 hrs and they also assume that there will be some ingestion of dust particles generated by removing the radium paint.

Repair Handling time
Repair Handling time

So I see a couple of problems with this model, so I am going to circle back around to it, in just a minute and apply some common sense to it.

Tools and Equipment

Now if you are going to be fooling around with vintage watches you are going to want to get a Geiger Counter.

 There are obviously tons of options when it comes to Geiger Counters but the best type of Geiger counter for detecting radium would be a Geiger-Müller (GM) tube-based Geiger counter. These counters are specifically designed to measure gamma and beta radiation.

The one I use is this GMC-300S. 

geiger counter GMC-300S
geiger counter GMC-300S

It has three different ways of measuring but the one I care about is this one that measures  uSv/h, microsieverts per hour,  because I can convert that into Millirems and Millirems is what’s used in the Timepiece Dose modeling reports, so now  I can make a direct comparison with my own testing results.

Now let’s look at a watch that has Radium. 

 This is a Gruen Veri Thin with your typical Radium hands. You can see that the Movement itself is not really picking up anything, but when we put the Geiger counter on just the watch hands…you can see that it’s picking up about 9 ½ microsieverts per hour.

If you take that 9.5 microsieverts and convert it Millirems you can see that it only equals a Dosage of .95 Millirems but if you multiply the exposure by 25 hrs as they did in the repair modeling you can see that it comes out to a dose of almost 24 Millirems.

24 mrem
24 mrem

Judging by the amount of radium paint on these two hands, what that tells me is that if  1 MIcroCurie of radium,  after 25 hrs of exposure, produces 15 Millirems of Dose and these two hands I measured and multiplied out over 25 hrs showed 24 mrems, then each watch hand is approximately 1 microcurie. 

Now if a single watch hand can have 1 microcurie of radium on it,  a watch dial with 12 painted numbers is probably going to have somewhere between 10 to 20 Microcuries of radium on it. 

If that were the case for a watch that you wear,  then the effective dose from wearing that wristwatch would jump up to somewhere between 600 to 1200 millirems of dosage per year, which is about twice to 3 times your normal environmental exposure,  but if you are carrying a pocket watch like that, the dosage would jump up to between 4800 to 9600 millirems per year which is the maximum dosage the NRC says is safe or up to twice the amount they say is safe. 

Removing Radium From Watch Hands

Now to remove radium paint from the watch hands, the way I do it is pretty simple and very safe. I just take 2 small disposable plastic cups with lids and add IPA.

cleaning Watch hands from Radium Paint
Cleaning Watch hands from Radium Paint

I drop the hands in the first one and just use a couple of tooth pics to remove the Radium Paint and I use the 2nd jar to just rinse the hands off.  After they dry a quick inspection under the microscope shows there’s no leftover lume.

Inspecting Watch Hands after cleaning off Radium Paint
Inspecting Watch Hands after cleaning off Radium Paint

By cleaning them in the IPA, it lessens any chance of dust being ingested and when I am done everything goes in a zip-lock bag and then out to the trash can. 

Now I know some of you are wondering about cleaning Radium numbers and that’s something I wouldn’t do but if you want to attempt it I would obviously wear gloves and also wear a facemask with a HEPA filter.

Now when I check the same hands again with the Geiger Counter, the microsievert is reduced to about .5 or .6 Microsieverts per hr.

 Geiger counter reading after cleaning off Radium Paint
Geiger counter reading after cleaning off Radium Paint

When you consider that your exposure, cleaning these hands is about 15 minutes at the most and not the 25 hrs used in the repair dosing model you can see that the Dose you might have received removing the Radium paint is pretty small overall. 

Even If you are working on a watch with radium on the dial and hands, if you use some common sense to limit your exposure to the Radium paint, you can safely work on these vintage watches and the because you now know more about the reality of Radium Watches and their safety, if you practice some of the tips I showed you,  it will make you a better and safer watchmaker.