Mike Gordon on tue 27 dec 11
I just ran across this about kiln viewing glasses, Mike Gordon
Begin forwarded message:
> From: Liz Gowen 1
> Date: August 18, 2011 6:23:06 AM PDT
> To: Clayart@LSV.CERAMICS.ORG
> Subject: FW: kiln glasses
> Reply-To: Liz Gowen 1
>
> 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
> every
> 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 as
> 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 did
> 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/Uvex
> _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!
>
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