Last year, I posted a question asking about anyone's experience regarding cleaning coins using an ultrasonic cleaner. As you would expect, I received a multitude of comments, some of which were completely off-topic and some of which were on topic. Several valid, IMHO, points were raised. So, I've been thinking about it ever since and decided to run some experiments. Being a design engineer, I first started thinking about the criteria. Here are those criteria: 1) The design had to hold the coin by the edge. 2) Coin had to be held by minimum of points, which is three. 3) Coin had to be held vertically so that it would not touch anything other the 3-point suspension and so that any dirt/grit/etc. would fall away from the coin and not abrade the coin. 4) Contact points to the coin must be softer than the coin metal. 5) All components must be compatible with 150F temperature, water/detergent mixture, acetone, and xylol. 6) Holder of the coin must not release the coin under the temperature and vibration induced the by ultrasonic cleaner. So, I finished the holder design and construction today. Photos below. The materials are steel, aluminum and lead. The little fixture holding the coin is a steel 8-32 hex coupler, turned to length and with a molten lead plug poured in the end. I also tested HDPE and nylon in acetone for several hours with no discernible degradation. At this point, I want to caution anyone who is tempted to use acetone, xylol or any other flammable solvent in an ultrasonic cleaner. These devices are not explosion-proof and when a volatile organic solvent is agitated by ultrasonics, its evaporation rate is increased. So, there is a not-insignificant chance of ignition. I have used acetone in this device but I do it outside and keep away from it, just in case. I do not endorse using flammable solvents in these devices! Back to the test: I then proceeded to test it with an out-of-pocket quarter just for functionality and in plain tap water. The ultrasonic cleaner is from Harbor Freight and it can raise the temperature up to about 160F. For this test, I raised it to only about 100F. Ran the ultrasonics for about 10 minutes total. Results so far: Holder does not release the coin. Pressure applied to the coin is pretty low so potential for bending a smaller and thinner coin is low. Further tests will be done on a old copper large cent, a bronze IHC and a silver coin. I have to see if I have one of each with deposits. I will take photos and closeups to try to determine if one of the concerns raised, the surface pitting that might occur from the implosion of the bubbles generated by the ultrasonic treatment, actually occurs. Also to be examined is efficacy of cleaning dirt and organic deposits, as well as seeing if the treatment spalls off toning. Part 2 later.
So uh, you got patent pending on it already...? It all seems like it would work really well and it's a good design, I cant wait to see some of the results!
Nice device. However, there is a much simpler and less "engineered" solution for under $15 and they'll last for decades if you take care of them: Wolfcraft plastic hobby clamps. Remove the yellow tip. The 2nd and 5th long nose are perfect. You need to hold the clamp in your hand - more control. Don't use in acetone!!
There are almost always multiple ways to skin any particular cat (apologies to Meow!). I dealt with this all the time in my working life - "Why don't we just do this?" Invariably, the suggestion had not been thought through adequately but I always listened respectfully because anyone who thinks they have all the answers is fooling themselves. I have a machine shop so I could make it to my specifications which most people cannot. My object is to be able to test in multiple solvents to see which things seem to work "best" and to determine if the coin is damaged in any discernible manner by the ultrasonic treatment. I really don't have any pre-conceived notions of how this will turn out. And I certainly will not and don't recommend doing this with a coin that has any significant value.
That's ironic, I was in Harbor Freight today and noticed that ultrasonic cleaner... I'm looking forward to before and after pictures...
Very very interesting. I love ingenuity and the simple elegance of the three point holder is spectacular. I will be awaiting part two.
Just trying to save you and others time, money, and ease of operation. I'd like to see a video of you putting a dollar sized coin into that contraption. Interestingly, we were talking about "Why not do this" last week as often times folks who are completely ignorant of what's going while watching a task being done by the professionals will come up with a suggestion that is perfect. I will not share some personal examples out of false modesty.
Unfortunately, the depth of the ultrasonic cleaner I have probably precludes doing it in this manner for a dollar-sized coin while keeping the coin vertical. Also, the size of the aluminum ring was dictated by the size of the raw material I had on hand. I can get it to half-dollar size, I think, but I haven't tried it yet. In any event, the research effort doesn't depend on the size of the coin.
Great for cleaning all kinds of things including your wife's jewelry. I also use it for cleaning my glasses. About 20 seconds in water with three or four drops of Dawn will remove the grunge from every crevice of your eyeglasses. Just make sure to re-tighten all the screws! Voice of experience.
