John Baymore on thu 9 jul 98
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It is my understanding that using inexpensive non-UV attenuating, non-IR
attenuating sunglasses as =22protection=22 from any damaging radiation =
coming
from the kiln can actually make the potential problem WORSE.
Your eye is not a receptor for either IR or UV....... it can't see and
respond to them. It responds only to the visible light waves. As the
intensity of visible light goes up, the iris of the eye closes down to
limit the amount of light reaching the interior structures like the aqueous
humor and the retina.
In the case of a glowing kiln... a lot of visible light is being emitted
along with a small amount of UV and even higher levels of IR. Because of
the visable light, the eye naturally tends to close down and limit the
light entering as you peer into the kiln with the naked eye. As a positive
by-product of this response, less UV and IR can enter the eye.
If you put a lens over the eye that cuts down the visible light waves
without limiting the UV and IR, the iris opens wider, and lets more of both
of these to enter the eye than would have without the dark lens. You have
the mistaken impression that you are doing a good thing...... since it
seems easier to see into the kiln. But you aren't.
How much damage you might actually sustain from firing kilns is a
complicated equation. Pretty hard for anyone to tell exactly. (There
still is no definitive PROOF that cigarrettes cause lung cancer =3Cwg=3E.)
Factors include genetic predisposition to having eye problems (luck of the
draw factor), frequency and duration of the exposure, the size of the
opening into the kiln you look into (the larger the greater the radiation
source), how close you get to the port (inverse square law), how hot the
kiln is (higher temps give off more UV and IR), how many years of exposure,
and so on.
Add into this occupational exposure, the exposures to IR and UV from all
other sources. The eye doesn't care if the source is the kiln......... or
the sun at 12,000 feet reflecting off snow at the top of Copper Mountain.
Certain types of occupational damage to the eyes from glowing furnaces is
pretty well documented. It is refered to as Glassblower's Cataracts.
Hot kiln refractories certainly do emit some UV along with the IR.
Mis-align an electronic UV detector from a flame safety system on to the
glowing brickwork, and it will still show a =22positive flame proof=22 even
without a flame present. This factor can be a problem in setting up
combustion safety systems. Is this UV significant as a health hazard? I
have never seen a study of potters and their kilns... so I don't think we
really know for sure.
A good simple defense against this type of potential problem is to get the
same safety glasses that glassblowers use. They have FAR more exposure
than we do (except maybe those of us who woodfire.) The lenses have a
weird name that I just can't think of as I sit here at the
computer...........I want to say something like =22neodymium=22...... but
that's not right. They stop both IR and UV. They aren't cheap, but they
are good protection. They can be gotten ground as a prescription lens.
Good sports sunglasses are rated to stop 100 percent of the SUN's UV
output.... but I don't know how they rate relative to a kiln's UV output.
Polycarbonate lenses inherently restrict UV..... at least at the level of
the sun..... and don't need special coatings. Neither stop significant IR,
to my knowledge.
Check out the info in =22Artist Beware=22 or the =22Health Hazards Manual =
for
Artists=22 for more detailed stuff on this subject from the health
specialists.
Best,
..........................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
603-654-2752
JBaymore=40Compuserve.com
Fay & Ralph Loewenthal on fri 10 jul 98
John glass workers use pink didymium glasses to cut out
the soda flare glare. All hot glass workers should use these
not just glass blowers. I believe they sell for around $50.00
a pair. I cannot get any here in South Africa. Hope this
helps Ralph in PE SA.
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