[Jewelry making - Article 00301] - Re: [Orchid] What is the value of an ultrasonic?

[The Doctor]

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>     Warning - don't put hands or fingers in the ultrasonic! The blood
>     in the veins and arteries of inserted body parts gets aerated and
>     forms tiny clots which can circulate and lodge in dangerous places
>     such as the brain. If this is a myth please debunk it. 

    It is no myth, at least in your intent. Ultrasonic cleaners cause a
    very real phenomenon called cavitation. In living tissue, it is
    specifically called non-inertial cavitation. While I don't believe it
    can cause clots or cause bubbles to lodge anywhere, the formation and
    subsequent contraction of the tiny voids (they're not actually
    bubbles) definitely causes energy in the form of heat and a wave of
    pressure that is quite detrimental to surrounding tissues. Even short
    term exposure to ultrasonic waves can cause a lot of discomfort as a
    curious coworker of mine found out. Long term exposure would be
    devastating. The energy caused by the formation and collapse of these
    voids is called "boiling," and the resultant heat, if the tissue is
    held in long enough, will do just that. 

>     because ultrasonics work by causing tiny bubbles to expand and
>     contract, and by so doing lifting the dirt off. We have all heard
>     what bubbles in the blood can do - the bends, clots caused by air
>     in injections 

    The bends, also known as decompression sickness, is most often
    contracted by divers who descend far enough and long enough to cause
    nitrogen to dissolve into their tissues due to the increased pressure
    at depth. If they ascend too quickly, the change in pressure is
    similar to opening a soft drink bottle. The nitrogen transfers
    rapidly from the tissues to the bloodstream. So rapidly that it can
    form bubbles of nitrogen and the very painful, sometimes fatal
    condition known as the bends. But I never heard of clotting caused by
    the bends. 

    A diver can avoid the bends by keeping track of air supply and
    leaving plenty of time for safety stops on the way up to allow their
    nitrogen-soaked tissues to exsolve. However, there's no way to
    prevent non-inertial cavitation when plunging one's hand into an
    ultrasonic, so please don't. 

James S. Duncan, G.G.
James in SoFL
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