[Jewelry making - Article 00265] - Re: [Orchid] Ultrasonic cleaner and damage to hands

[Anne Larsen Hollerbach]

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    Hello all, There is a HUGE difference between the frequencies used by
    ultrasonic cleaners and ultrasound medical equipment. 

    And yes, you can certainly hurt yourself in an ultrasonic. 

    When my cousin was finishing her degree at the School of Mines in
    Golden, CO, one of her classmates was rushing to complete the
    preparation of hundreds of thin section specimens of minerals for
    his master's thesis. He was working long hours and running right up
    against his deadline. One evening he just figured that it was
    ridiculous to have to fish around in the ultrasonic cleaning chamber
    for his rock slices which were wickedly difficult to catch with the
    big tweezers he had. So he just reached in and fished the slices
    out. He did this many, many times that night with the big ultrasonic
    tank on the entire time. This was in direct violation of stated
    safety policy of the department, which was posted on big signs
    around the lab. 

    By the next morning he could not hold a pencil, his fingertips hurt
    so badly. They were bright pink and starting to look puffy. Finally
    he went over to the school clinic and they checked him over. When he
    told them what he's been doing, they took an x-ray. He had
    thoroughly destroyed the bones in this fingertips -- they showed up
    as gray ghosts on the film, not nice, tight, white bones. Basically,
    the doctor told him that the sound waves had given him the most
    complete set of stress fractures he'd ever seen. Not to mention the
    soft tissue damage -- the pinkness and swelling was due to bleeding
    deep in the tissue. 

    It took a long, long time to heal, and wow, did it hurt like hell. 

    Don't go there. 

    I realize that an anecdote is not convincing for many folks, so I
    went looking for more detailed safety discussions on the kind of
    ultrasound we use in our cleaners. To my chagrin, there is very
    little out there. There is an excellent general FAQ on ultrasonic
    cleaners and how they work at 	cleansonic.com/ultrasonic_faq.htm This
    explains the physics of cavitation nicely in layperson's terms. You
    will have a much better understanding of what your cleaner is doing
    (or not doing) and why you need to have some kind of detergent in
    the water in order to accomplish anything. To check if your cleaner
    is working properly, you can immerse a little square of aluminum
    foil suspended from a bit of wire, and in a few minutes you should
    have nice little perforations all over the foil. This site explains
    the procedure nicely, and yes, it surely does work. And it certainly
    illustrates how vigorous the energy in that little tank really is:
    strong enough to shake bits of aluminum right out of their nests.
    Ever dropped in pearl and watched what happened? Since the sound
    waves travel especially well in liquids, and you are basically a
    liquid in a sack made of skin, you can see how there is a potential
    problem here. 

    As for the issue of tissue damage, check out the "Guidelines for the
    Safe Use of Ultrasound, Part II -- Industrial and Commercial" at the
    Canadian government's informative Consumer & Clinical Radiation
    Protection site. Specifically:
    	www.hc-sc.gc.ca/hecs-sesc/ccrpb/publication/safety_code24/toc.htm
    Click on the "contact exposure" headings. They do mention the
    scarcity of research on this topic. There has been one study with
    volunteers, who did confirm that putting your fingers in a tank can
    hurt. (I would suspect that there are ethics problems in pursuing
    this further with human subjects.) The article says: 

    	"Contact exposure can in some cases provide nearly 100% energy
    transfer to tissue... For example, high-power ultrasonic waves are
    used in ultrasonic cleaners and cell disintegrators because of their
    destructive and violent effects. It is certainly reasonable to
    assume that relatively intense cavitation activity occurs in the
    water (or solvent) baths of such devices.... 	"The literature on
    devices such as ultrasonic cleaners and tissue homogenizers is
    confusing: these devices do not appear to be as hazardous as
    expected, given the effects they were designed to create.
    Nonetheless, although reports of biological effects are surprisingly
    rare, exposure to the liquid-bourne ultrasound from these devices
    clearly can cause tissue injury, and protection measures are
    necessary." 

    In conclusion, this is not an urban legend. This is physics. Renate,
    please stop using your ultrasonic tank to clean your fingers. Just
    because it "feels much the same" as medical ultrasound: it is not,
    and this is not a safe practice. 

Anne Hollerbach


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