Ultrasonic cleaner and damage to hands

Hi all, Just a quick question for my workplace. Today I was holding
the trees from the cast over the ultrasonic (by the bottom) as I
always do after the trees from a cast have been blasted clean. One
of the jewellers told me that if I continued to do that over a long
period of time the vibrations from the ultrasonic would damage the
cartilege in my hands. My team leader however disagreed saying that
that risk is only present if you put your hands in the water of the
ultrasonic. I just need to find out which of these is correct so
that I can make sure I’m not putting my long term health in jeopardy
in any way. Thanks.


Hi Tina,

Ultrasonic vibrations of more than about 50kHz travelling through
air are attenuated so heavily that they are effectively not
transmitted at all (that’s why they use that jelly-like substance
when they use ultrasound to image foetuses - it conducts the sound.)
In practical terms, this means that ultrasonic cleaners pose no risk
unless you (a) put your hands into the water, or (b) hold the item
you’re cleaning whilst it’s in the water (because it conducts the
ultrasonic vibrations into your hand.) Ultrasonic vibrations can
cause serious damage: ship screws (propellers) are frequently pitted
on the forward side due to ultrasonic boiling of the metal. Hope
this helps, DM –

Thanks for you help Danny. Just one more question - currently we
ultrasonic the trees after the cast by holding onto the bottom of
the tree and dangling it in the water. From what you’ve said it
sounds like this is not a good practice. We also have a hook to
hook the tree onto and then dangle it in the water holding the other
end of the hook in the hand. Is this as bad as holding the tree
itself? Should we develop a way to hang the tree in the water
without needing to hold anything at all? It would not be impossible
to do such a thing but I would need to convince my superiors that
there is a health and safety risk to be allowed to spend the time on


Why can’t you just put the trees in a metal basket that fits in the
ultrasonic? Standing there holding it doesn’t seem like a good use
of your time. Jan

    Why can't you just put the trees in a metal basket that fits
in the ultrasonic? Standing there holding it doesn't seem like a
good use of your time. Jan 

OK boys and girls… Once more with feeling, YOU DO NOT PUT ANY
RUNNING!!!AS you know ultrasonics clean by a process known as
cavitation. In order to do this effectivley the liquid must be
degassed. That is the removal of all disolved gasses in the liquid
be it a soapy water solution or the blood in your body parts. It
also attacks the fluid in the joints of your fingers or any other
joint you stick into the tank while it is running. Sorry about the
shouting but common sense should be the guide here.

Mike & Dale
Lone Star Technical Service, The ultrasonic repair guys

Thank you Mike and Dale for your reply. Somehow my original
question has been lost here and still has not been answered. I was
not asking if putting your hands in the ultrasonic was bad as I was
already aware that it was. The question is, is it damaging for
your hands to be holding something that is immersed in the
ultrasonic water without the part you’re holding being immersed? My
guess would’ve been that it was okay to be holding something into
the water as long as your hands don’t come into contact with it. As
a jeweller has told me that it can damage your hands to even do that
I am a little concerned and would like to get to the bottom of this
issue. I asked my production manager if he knew where I could find
out if this was true or not and he first told me it wasn’t true…
then perhaps remembering the recent health and safety overhaul we’ve
had and how him dismissing something could be seen as neglectful he
rethought it and said, no, he didn’t think so but he would talk to
the jeweller in question.

When I first arrived at this workplace and started working in
casting I had read a lot about the risks associated with investment.
We worked directly with it - no masks, no gloves … no protective
equipment of any kind. I explained the risks I knew of to my team
leader who in turn laughed at me. Since the place has been swept by
health and safety officers we have been issued with masks, gloves
and safety glasses to be worn during all processes involving
investment… this incident alone makes me not trust the people in
positions of authority in my workplace to look out for my best
interests when it comes to health and safety. This is why I am
asking this question here - I want to be sure that what I do as a
part of my everyday work procedures is not going to compromise my
health and I know I can’t be sure of the answers I am given at work.

Thanks all for your replies, its really appreciated.

 The question is, is it damaging for your hands to be ho=


something that is immersed in the ultrasonic water without the
part you're holding being immersed? 


We have so many chemists in the group I’m surprised we don’t seem to
have any physicists speaking up about sound transmission or the
damage potenial of ultrasound after traveling through a solid.

Some food for thought:- While I can not say for certain what
ultrasound will do to your body after traveling through the cleaner
and your solid part; I can say for certain that sound travels
through solids more effeciently than through air and thus ultrasound
has the potential to be damaging after traveling through your casting
tree even if the portion of it that you are grasping is not within
the solution. As an example of the principle: auto mechanics will
use a dowel or metal rod held to their ear to move about an engine to
pin point the source location of an engine noise.Try it, it really
works…just be careful to avoid any moving parts! Perhaps if your
casting tree were hung loosley from something else (a wire, tongs,
etc.) the loose jointing would reduce transmission of the sound wave
to your hand enough to avoid damage, if in fact damage can occur in
that way. I’m not a physicist or ultrasound engineer, I’m just
remembering some long ago college physics leason.

Paul D. Reilly
The Paul Reilly Company
4308 Driftwood Drive Colorado Springs,
Phone: 719-598-9307 Fax: 719-592-0794
Email: @Paul_D_Reilly1

Could someone be willing to share the source of what I believe to be
an urban legend relating to the “damage” caused by ultrasonic
cleaners to hands? I have done plenty of foolish things in my day,
but I don’t believe that I have suffered any, might I ephasize, “ANY”
damage in 34 years of cleaning my hands in ultrasonic cleaners of the
size and types usually used to clean jewelry.

I won’t make the same claims about some of my other habits and
practices, but I really don’t think that an ultrasonic cleaner is
something to be scared of and I can find no reliable cites on the net
to contradict me.

Bruce D. Holmgrain
JA Certified Master Bench Jeweler

I don’t believe there is enough energy available to be transmitted
to your hands holding a part immersed in a normal ultrasonic
cleaning bath. ( wow!) Ultrasound is used as a safe diagnostic tool
. Focused high energy level ultrasound is used to treat tumors. For
a simple web article:


As in all things caution is better than recklessness.


Hi Bruce,

It is not a legend here is a quote from a FAQ page of an ultrasonic

manufacturer (http://www.soniclean.com.au/FAQ.htm#hands)

Q: Can I put my hands into the water when my ultrasonic cleaner is

A: As part of the occupational health and safety, no part of the
operator’s body should be submerged into the water during operation
as the ultrasonic energy is enough to cause damage to joint tissues
and result in long-term arthritic conditions.

I looked at other operators manuals and data sheets on the web and
all of them say in one form or another not to put any part of your
body in the tank while it is operating. The one above was the most
specific as to the danger posed. I am sure that most manufacturers
don’t list all the effects to limit law suits.

When I was in the Navy we had a large (about 1 cubic foot tank)
ultrasonic cleaner for parts cleaning. The operators safety
instructions included warnings about gas bubbles in the blood and
joint deterioration from immersing your hands in the tank while
operating. While this was a more powerful machine than the ones we
use I think I will continue not to put my hands in the tank when it
is on.

Jim Binnion

James Binnion Metal Arts
Phone (360) 756-6550
Toll Free (877) 408 7287
Fax (360) 756-2160

Member of the Better Business Bureau


Yes holding onto something that is immersed in the ultrasonic can
cause problems as well. It will depend on what you are holding on
to; metals or glass will conduct the energy much better than
plastics are your hands wet or dry there are many variables. The
ultrasonics energy will not couple quite as well into your body from
holding onto something so there will not be as much damage but it is
still a bad idea. This is why there are baskets, beakers, racks and
strainers sold to hold items in ultrasonic cleaners. – Jim Binnion

James Binnion Metal Arts
Phone (360) 756-6550
Toll Free (877) 408 7287
Fax (360) 756-2160

Member of the Better Business Bureau

I too would like an answer to the question put by Bruce Holmgrain.
who said

    Could someone be willing to share the source of what I believe
to be an urban legend relating to the "damage" caused by
ultrasonic cleaners to hands?..... 

Ultrasounds are used in many medical instances. I’ve done many
ultrasound treatments myself on Physio patients in previous jobs as
physiotherapist’s assistant and receptionist. Many women undergo
ultrasound scans during pregnancy etc etc.

Having both done the physio ultrasounds on myself and stuck my
fingers in the jewellery cleaning ultrasound (great way to clean the
fingers) I can say they feel much the same. Now I would imagine that
different frequencies would be used for different purposes and would
be interested to hear if someone does have more technical info on
this subject.

Cheers, Renate

Jesse. Good cite! I might point out that this reference medical
insrtuments and ends with: " However, the intensity threshold for
cavitation in man is much higher than that obtainable by commercial
instruments (approx. 1 kW/cm2), and even though thermal and
mechanical effects may act synergistically, no confirmed bioeffects
in patients (or operators) have ever been observed. "

I wish I knew how to compare the volume of our cleaners with the
references to Watts/cm^2 as the volume of our cleaners would be best
described with Watts/cm^3.

Well I must agree with Bruce. I also clean my fingers in the
ultrasonic. (less often lately because of these posts) Is it bad for
you? I don’t know but it sure gets the rouge off well. If there is a
true health risk that is known we would all appreciate hearing it.
Otherwise, I will chalk this up to an urban legend also. (since I live
in the suburbs…I’ll only do it a little…)

Unfortunately, I would imagine for liability reasons, we won’t hear
from anyone saying it is a safe practice.


So far unless I have missed a post no one has reported real life
problem resulting in hand or fingers being in an ultrasonic.

I agree with Bruce Holmgrain. I have for the past 31 years cleaned
my fingers and hand in the larger more powerful professional jewelry
ultrasonics. Not only cleaning my hands after polishing but on the
weekend after working on cars I cant wait to get into my store on
Monday to get my hand completely clean of all the automotive grease
and grim.

Now I don’t just stick my whole hand in the tank and leave it in
there until it is clean. I dip my fingertip and sometimes my whole
hand for a few seconds, enough to loosen the polishing compounds or
the automotive grim, then I scrub.

Just like all warning being posted on products It is the
manufactures throwing a blanket disclaimer to cover any liability. I
don’t blame them with all sue happy people out there,

With happy hands
Jeff Dunnington

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:
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

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

dangers associated with ultrasonic cleaners

Hi there, In answer to Tina Duffy’s question about ultrasonic

My conclusion:

there are defatting problems and dermatis issues from the
solutions-keep youf fingers out and use tweezers. In terms of damage
to joints, the medical ultrasounds are finely tuned to not hurt the
body, I don’t believe jewelers ones, which age, and are altered by
what is in the tank and how the tank surface is corroded etc are as
controllable or as constant in their output. It’s purpose is to cause
cavitation, bubbles which appear on the surface of the material, I
would suspect not good for you if it occurs inside your body…

my conclusion-don’t stick your fingers in the ultrasonic. Its no big
deal to learn to use tweezers and if it does actually hurt you then
you removed any risk by not doing it. And you’ll lessen your chance
of skin damage. best Charles here are bits from the safety book.

Ultrasonic cleaning equipment can produce headaches, dizziness and
nausea in some people (Kinnersly 60).

Ultrasonic Cleaner

See all the general safety rules above and the grinder rules as
well, as most apply here. Follow all the rules about electricity very
carefully. Electrocution and fire are always possible when using
electricity. Don’t operate the machine unless the tank is at least
half full of liquid (or better, almost full and regularly topped up
to the right level). Don’t overload the tank or place heavy work
directly on the bottom, as this will decrease its efficiency. Don’t
use volatile, toxic, or inflammable solvents in the ultrasonic
because the use of ultrasonics tends to increase the evaporation
rate and cause additional hazards. Use tweezers to place objects into
the tank, and to remove them. This keeps your fingers out of the
cleaning solutions with their de-fatting effect, and keeps them away
from the ultrasound as well. If your ultrasonic is very noisy,
consider segregating it behind some kind of barrier-high-pitched
sounds are the most damaging to your ears. When you are finished
using the machine, rinse the tank well and wipe it dry.

Ultrasonic Cleaning

Jewelers use ultrasonic cleaning to remove grease and polishing
compounds. Sometimes in order to strip investment from castings, an
acid solution is placed in a beaker and placed into the fluid in the
ultrasonic. Hazards: See the section in “Rules for Tools” on
ultrasonics. Electrical hazards are present. Noise can be an irritant
and high-pitched ones may be damaging. Dermatitis from exposure to
degreasers and detergents. People have worried about putting their
fingers into the ultrasonic for some time; there are rumors that it
damages one’s joints over time. I have seen some debate about this.
Acids used for investment removal can be dangerous-see “Acid
Handling.” Chemical: My main worry would be the “defatting” of the
fingers by exposure to cleaning and degreasing compounds. Defatting
results in “dry, scaly, cracked skin” (McCann, Health Hazards 23),
and makes you more susceptible to absorbing chemicals through your
skin and reacting to metals. Acids and alkalis may be used with
ultrasonics, though in beakers within the ultrasonic rather than in
the bath itself. This can cause mists-an issue. Physical:
Electrocution, noise may be an issue. Ergonomic: Working heights,
production usage are the main concerns. FiRe: See “Fire Safety Rules”
and “Fire Safety.” Electrical fire is a possibility with powered
equipment. Avoid using flammable solvents in the ultrasonic cleaner,
even if they are in a jar placed in the liquid in the ultrasonic.
Exposure routes: Hearing, skin, inhalation of chemical cleaning
mixtures. Safety precautions to use: Use your tweezers as much as
possible to keep your fingers away from the chemicals, soaps,
solvents you use. I wear my 8-inch German, stainless steel tweezers
in the center pocket of my apron, always at hand when I need them.
Keep a pair of tweezers as part of your apron or jump suit, then you
will be less likely to use your hands when you shouldn’t. Sound
levels may be difficult to bear depending on the machine. Get the
quietist machine you can. Substitution options to reduce risk:
Ultrasonic cleaning is itself a safer substitute for various solvent
uses. Dishwashing liquid, a toothbrush, a little household ammonia
and hot water in a stainless steel pan on a hot plate does a pretty
good job. The “Speed-Brite” ionic cleaner substitutes for some
ultrasonic functions.

Charles Lewton-Brain/Brain Press Box 1624, Ste M, Calgary, Alberta,
T2P 2L7, Canada Tel: 403-263-3955 Fax: 403-283-9053 Email:

Our Collaborative site to benefit the worlds’ jewelers:

Over 500 pages of Charles’ writing:

Book and Video descriptions:http://www.ganoksin.com/kosana/brain/brain.htm
Gallery page at: http://www.ganoksin.com/brain/gallery.htm

no one mentioned this, take a piece of aluminum foil, sheet, place
in the ultrasound, one for 30 sec and one for 1 minute. hearing
about this and doing this has kept my hands out of the ultrasonic.
one can only imagine that the damage from placing your hands in the
ultrasonic is accumulative over the years.


Hi James.

    It is not a legend here is a quote from a FAQ page of an
ultrasonic manufacturer (http://www.soniclean.com.au/FAQ.htm#hands)

I have not doubt that these warnings come with good intentions,
however, they do not cite any medical or scientific data or
to back up their info. It is not uncommon for
manufacturers to be overly safety aware with the looming dangers of

     I am sure that most manufacturers don't list all the effects
to limit law suits. 

Why would you think that?

    When I was in the Navy we had a large (about 1 cubic foot
tank) ultrasonic cleaner for parts cleaning. The operators safety
instructions included warnings about gas bubbles in the blood and
joint deterioration from immersing your hands in the tank while
operating. While this was a more powerful machine than the ones we
use I think I will continue not to put my hands in the tank when
it is on. 

I might be mistake, but I believe that these machines are powerfull
enough to remove most deposits without even using solvents. Is that
wrong? How many watts were these machines butning? Is it really fair
to include them for comparison to the machines that most jewelers use?

I don’t believe there is enough energy available to be transmitted
to your hands holding a part immersed in a normal ultrasonic
cleaning bath.

Fine, so you can stand there and hold on to it; but either way I’d
prefer to drop it into a basket or put it on a coat hanger wire hook
and get back to my bench. To each his own. Mark Kaplan