Re: Static disCharges: For Rent, Lease or Purchase
|From:||"Monson, Frederick C." |
The last time static was a problem for me was right after my wife and I were
married and we had this "SPECIAL" carpeting in the bedroom of the apartment
we occupied. Thus was I introduced to the mating of biology and physics.
I recall that at that time I treated static as a pain in the donkey! It
wasn't until after the humor of it all set in that I began to see that
science was involved in our predicament. I recalled having had problems
with static while sectioning, and I always blamed the microtome. The
solution to OUR problem was rooted in solving the differences in charge
between US!!! Entering the bedroom required that we hold hands when doing
so, thus, all spontaneity was lost and we were rapidly reduced to routine
and negotiated meetings - if we were to continue treating the bedroom as
predicated in the agreement made with our parents before we were joined.
Thus did I learn why one was well-advised to delay children until after
marriage. With children, one could not readily and thoroughly investigate
the science of every room in the home, and one would miss storing up
memories that are simply not possible to obtain in any other circumstance.
Again, it wasn't 'til much later, when I had time to consider sectioning
again, that I realized that the poor microtome was an innocent bystander -
If the reader wishes to recapture any of his or her day by skipping to the
end, do so and get to the suggestion for amelioration of the static that has
developed to this point between us. That is, GOTO END. For those who need
a deeper scientific understanding of static, the interim is offered without
apology, and hopefully without too much error.
Here's the scenario. Mary Jane, wearing a 'special' new lab coat and
'special' new shoes has been swishing and swirling throughout the lab for
about an hour. She has been positively snapping her way through the lab.
Her job is to collect this and that periodically during the day and transfer
them to wherever required. Finally she gets to the sectioning room and
stops to say hello to Harry, who has been trying to date her for months and
to whom she has always said. "No!". While talking with Harry, so he can ask
her out again, she leans against the cryostat which is conveniently near.
After providing Harry with his negative for the day, Mary Jane leaves the
lab. Moments later Debby arrives at the cryostat with a frozen specimen to
section. The specimen is locked in the chuck and the sections begin to fly.
Debby says, "Darn!" and glides over to a nearby bench to get some water.
Swishing and a-swirling, swinging and a-dancing, Debby applies the water in
drops, mist and gushes. She turns the crank while her sleeves rub against
the body of HER 'special' lab coat and against the crank and the box and
then against the interior of the box when she reaches in with the slide.
While watching Debby struggle, her supervisor, originally a physics major,
opines that the environment is really less humid than is optimal, so he puts
a large container of water on a hot plate to re-humidify the air. Debby
finds no repair to her problem throughout the day. She reflects on how nice
it is that Mary Jane stops by so often to commiserate with her as she works
from one aggravation to another.
Static charge, measured in coulombs, can become a very bothersome voltage
discharge in the bedroom, the family room, or the workplace. But if there
are no sparks, we think of static differently. No sparks, no discharge.
Aren't we funny, we humans! With respect to static below the level of a
discharge as a serious impediment to sectioning, I offer the following.
If one has to treat the cryostat box, then I suggest that the machine may be
improperly grounded electrically, or that the box, usually steel, is not
grounded at all.
If, on the other hand, the slide has to be treated, or one has to blow,
puff, or otherwise expel moist air into the chamber to keep sections from
"flying" to the slide, then the slide is improperly grounded, and probably
also otherwise contaminated. Can one ground the slide by grounding the
If, the slide appears to be improperly grounded whenever the operator is
wearing certain shoes, then I submit we have to conclude that the operator
is improperly grounded in those shoes, or the shoes are a static charge
generator with something that the shoe rubs against in the environment. On
the other hand, if the operator is no less grounded when wearing other shoes
and the slide is not charged, what is one to do when one wears those
'special' shoes? One doesn't think that giving the slide a quick rub with
that paper towel before use can cause any harm. One does it whether wearing
THOSE shoes or others.
When computer technicians work on computers, they are often admonished to
properly ground themselves to insure that their static charge is properly
dissipated. They comply with this admonition by wearing a bracelet
available at Radio Shack, by which they are attached to a ground so static
charge will continuously be dissipated to ground instead of building up and
causing a snap when he/she picks up the new Pentium XXV, 42GHz CPU for which
the customer is paying $42, including installation! In some large offices,
with certain combinations of shoes and carpet, computers are in constant
danger! Why the continual requirement for grounding? Well static arises
from friction and friction only occurs between things that rub against one
another, so there must be constant static generation while the technician
works on the computer. Clothes against clothes, shoes moved over the floor,
clothes against chair, hands rubbed on trousers, hands thru hair, and so
forth. Even Charlie coming by to grab the desk and say hello.
It seems to me that if one can determine what component of a system is
continuously building up a static charge, then one can determine which
component to ground. The computer folks have gotten the message. For
example, Harry (from the above scenario) simply can't do frozen sections.
Absolutely nothing can help when Harry and the cryostat get together, so
Harry has other assignments in the lab. No one, least of all Harry,
remembers that Harry was a fine sectioner before Mary Jane started working
at the lab, and no one has every found Harry's frenetic fidgeting when Mary
Jane dropped by wherever he was when she dropped by. No one ever considered
either grounding Harry OR Mary Jane to help ameliorate the problem with
Harry! If only Harry hadn't met Mary Jane!
Static becomes a problem when it has no outlet. Another confluence of
biology and physics. Any object that collects a charge above ambient is
acting like a capacitor. The insulator is the air. If the air were a
conductor - ionized???, then there would never be any sparks between husband
and wife in those bedrooms with 'special' carpets. Since air is not, we
become mobile capacitors of static charge, just waiting for an opportunity
to discharge on contact - capacitively. I recall vividly that whenever such
discharges on contact occurred, I would laugh but my wife would complain.
She never got used to static discharges.
As a first approximation, one might suggest that a shroud of heavy-duty Al
foil, draped over the edge of the cryostat chamber and connected by a secure
electrical connection to a nearby ground - preferably a real ground, could
serve the purpose nicely if grasped by the operator prior to and during the
introduction of his or her statically charged other hand into the chamber.
The simple touch by the electrified operator of the microtome and the charge
is transferred, thus causing ribbons to wave and sections to fly. One
might, alternatively, experiment with grounding connections using insulated
copper wires with pinch-clamps on each end connected from the knife, the
microtome, the chamber wall and holding rack to a nearby water pipe.
While ionizing humid air in the cryostat chamber would provide a conduit for
static charge on the microtome and knife to dissipate, it might be possible
that a highly charged operator could dissipate his/her charge right back
into the unit after walking beck from the water cooler on those certain
special shoes while wearing that special lab coat.
So, what is the solution. One could stop wearing clothes and shoes that are
especially good at generating static in us, and one could do something to
change the ease with which certain environmental components generate static
in us when we move through them. Harry could recognize that getting all
charged up when Mary Jane was around was deleteriously affecting his work
and capacity to perform. If Harry had only discharged to ground every time
Mary Jane departed, he would have been fine. Poor fellow never understood
the physics of the problem.
The following URL is the address for a company with which I have no
relationship of any kind. If we treat static as a scientific phenomenon,
then perhaps we can understand it and even control it. URL:
Good humor is contagious and sometimes shocking!!! Also, always check the
carpets in the bedroom before you rent an apartment or buy a house, but
then, as one who has been married for almost 37 years should amend, don't
let the carpet in one room deter you from renting the apartment of your
dreams! You could be in for a much better time than you ever imagined.
Regards to all,
Frederick C. Monson, PhD
Center for Advanced Scientific Imaging(CASI)
West Chester University of Pennsylvania
Schmucker Science Center II
CASI Home Page: http://darwin.wcupa.edu/casi/
South Church Street
West Chester, PA, 19383
Please call before visiting
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