Liz Gowen 1 on thu 18 aug 11
Sorry I approved this message but it seems not to have been posted. I am
resending it since I think it took time and research to help clarify the
discussion on kiln glasses..Liz Gowen
Subject: kiln glasses
Okay, so David says welding glasses aren't enough, and you need buy pricey
didymium, but he doesn't have the time to look up all the references which
prove his point. Sadly, I don't have the time either, but the spread of
misinformation annoys me too much when people are spreading misplaced fear.
"Your eyes are too precious to risk" is not a solid foundation for an
argument, especially when, after doing the research, we'll discover that
plain didymium is *less* suited to this task than #3 welding glasses.
If you look at Uvex's line of safety glass materials
(http://www.uvex.us/uvexlenstechnology.aspx?id=3D4178), you'll find that ev=
ery
single one of them blocks over 99.9% UV except one... the didymium lenses.
Uncoated didymium blocks 80% of the UV spectrum naturally... but only 80%
without special coatings that increase the price. Didymium is a
naturally-occuring compound of neodymium and praseodymium... it is not a
material specially-formulated for the glass-blowing industry, it was simply
discovered in the 1800's and found to have a useful property glass working.
http://en.wikipedia.org/wiki/Didymium (Do note that this article has no
citations or references. Finding clearly reliable information about
didymium turned out to be difficult. I'm assuming that Uvex's claim that
their didymium lenses block 80% UV is typical of didymium, since it's a
standard compound... so reliable in its spectral filtering that it's used a=
s
a calibration standard.)
The primary purpose of didymium in glass working is to filter "sodium
flare," the visible yellow flame created when heating glass, so the glass
worker can see what's going on. It just coincidentally filters the narrow
band of light produced by sodium flare without filtering the visible light
around that band. Gas-welding aluminum creates the same sodium flare, and
didymium lenses borrowed from the glass working industry were used at one
time until they were *replaced* in the welding industry because didymium di=
d
not block enough IR.
http://en.wikipedia.org/wiki/Oxy-fuel_welding_and_cutting
Electric arc welding produces a lot of UV... enough to causes "sunburn" to
exposed skin (discovered from personal experience working with welders at
Boeing). http://en.wikipedia.org/wiki/Arc_welding
Proper arc welding glasses block UV. They block IR. They have to, or they
wouldn't be doing the job welders need them to do.
The glasses I pointed to earlier, the ones I purchased, are:
Uvex S1907 Skyper Safety Eyewear, Shade 3.0 Infra-Dura Ultra-Dura Hardcoat
Lens
They are made of Uvex Infra-Dura 3.0 material. This material passes only
14% visible light. Absorbs greater than 99.9% UV. Absorbs 91% of IR.
Conforms to ANSI requirements for protective eyewear.
http://www.uvex.us/uploadedFiles/ProductConfiguration/ProductLiterature/Uve=
x
_Lens_Tech_Update2011.pdf
All of this protection cost me less than $15, and it provides superior
protection for both UV and IR compared to didymium. The only thing it
doesn't provide is filtering of soda flare, which isn't a pottery problem.
They may or may not be ideal for making cones more visible, but that's not
the issue under scrutiny.
Whether an electric, gas or wood kiln produces UV or not is a moot point,
unless you're using uncoated didymium.
I see no reason to buy expensive didymium glasses to view the inside of a
kiln. Doing so will result in less protection than welding glasses unless
you buy the more expensive ones with the right coatings to make up for
didymium's natural lack.
I'm open to being proven wrong... but if you want to disagree with me, take
the time to provide references. When dealing with safety, lets deal in
facts, not speculation, folklore, poor memory or wishful thinking. To deal
in anything else is pointless and needlessly time-consuming.
Now somebody owes me a beer. I'm thirsty after 1.5 hours of research and
writing. :)
--
Carl D Cravens (raven@phoenyx.net)
Hail to the sun god, He sure is a fun god, Ra! Ra! Ra!
Steve Slatin on thu 18 aug 11
Carl -- I'll volunteer to buy you the beer. (I'm
hoping to make NCECA next spring, if that provides an
opportunity.)
Thanks for doing the work and finding actual references,
which the rest of us can pursue, if we wish.=3D20
FWIW, I don't think anyone specifically provides erroneous
information on safety, but people do provide summaries=3D20
and interpretations based on their own reading of information
or recollection of what they were told at some time in=3D20
the past by some person who they regarded as an authority.
Steve Slatin --=3D20
N48.0886450
W123.1420482
--- On Thu, 8/18/11, Liz Gowen 1 wrote:
>=3D20
> Okay, so David says welding glasses aren't enough, and you
> need buy pricey
> didymium, but he doesn't have the time to look up all the
> references which
> prove his point.=3DA0 Sadly, I don't have the time either,
> but the spread of
> misinformation annoys me too much when people are spreading
> misplaced fear.
> "Your eyes are too precious to risk" is not a solid
> foundation for an
> argument, especially when, after doing the research, we'll
> discover that
> plain didymium is *less* suited to this task than #3
> welding glasses.
>=3D20
>=3D20
> Now somebody owes me a beer.=3DA0 I'm thirsty after 1.5
> hours of research and
> writing. :)
>=3D20
>=3D20
>
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