[TheForge] FW: Didymium? I say "no way."

Thu Feb 9 12:34:54 EST 2006

To Mike Spencer,
During world war two, Cobalt light filters were borrowed from the foundry 
industry and used by oxy-acetylene aircraft welders to create an adequate 
view for gas welding aluminum. As you pointed out, blue filters wipe out the 
yellow and red bands of the spectrum. That includes every wave length longer 
than blue-green in the visible color spectrum, just into near infrared. The 
first advantage was complete suppression of "sodium flare." The flux used 
with aluminum was heavy in sodium and potassium which, when it flared up 
under torch heat, pretty well wiped out the view with ordinary green 
filters. Secondly, any blue or red filter will cut out about one-half of the 
color spectrum (and certain yellow filters will cut out blue). The range of 
the visible spectrum is 400nm to 700nm for most people and 380nm to 780nm 
for a few people; well somewhere between 750nm and 780nm. The exact number 
has been disputed for decades. Different light bands--wave lengths--bend at 
different angles through lenses, including the lenses in our eyes. This 
creates a double image, which our brains have to work overtime at sorting 
out. Blue, some yellows, and red, are all capable of cutting out enough of 
the color spectrum to sharpen the image impinging on our retinas, allowing 
the brain to get on with more important tasks, like interpreting what we see 
more clearly. Thus, cobalt blue filters became well known for showing a 
clear sharp image, while suppressing surface glare. That includes the glare 
of aluminum, platinum, and silver surfaces, along with the glare of highly 
radiant surfaces like furnace interiors.

By the early sixties, these aircraft welders were showing up with cataracts 
and other vision problems in droves, because straight cobalt did not block 
most of the IR range--cobalt welding filters were quietly withdrawn from the 
general U.S. marketplace completely by 1967. Today, cobalt filters are still 
used in foundries under "special use" (interpret that as restricted use) 
Table 2 conditions of ANSI pamphlet Z87.1-2003 recommendations (enforced by 
NIOSH), for viewing done for a limited amount of time only. So called Cobalt 
welding filters on the general market today are ANSI rated green glass or 
plastic filters with blue cobalt tint added to glass and dark blue dye added 
to the plastic variety. The plastic filter is about $57; although sold as a 
shade five rating, their view is more like a shade seven (the view through 
them SUCKS). There are also real cobalt flip-up glasses over shade 3 & 5 
ANSI rated green glass safety spectacles on the market (the view through 
them isn't exactly wonderful either, and they cost $35 to$39). Now, here's 
the funny part: Iron oxide, in small amounts is used as the first line of 
defense in green glass ANSI rated welding filters, heat-absorbing window 
glass, and the much more (like hideously) expensive optical grade 
heat-absorbing glasses. Beyond the iron oxide, IR suppression is tied to the 
filter's darkness. So, you would think that cobalt blue glass used today 
would have at least this iron oxide protection in it, right? However, I have 
not found any indication of such a product for sale. This doesn't mean the 
product isn't there--it means nobody is talking.

The only product for sale (along these lines) worth a tinker's d...worth 
buying anyway, is the TM 2000 Gas Welding Lens. Trouble is it costs $105 
dollars before taxes & shipping charges. I have one, and it is a 'Jim Dandy' 
special use green lens. It isn't a blue lens, or a yellow lens, or a red 
lens. It isn't a shade #1, #2, #3, #4, and #5 variable lens. You have to 
take some responsibility and work harder to get what you want if, like me, 
you're greedy. I want all the above, because I intend to control my view and 
enhance it as much as possible for an old guy with crummy vision. Just about 
everybody in the modern world has heard the phrase "good hand/eye 
coordination." It's one of those barely true, but very over used ploys like 
"team player" that are bandied about by people who's agenda is manipulation 
(they call it management of course). The truth is that, for almost all the 
people almost all the time, good hand/eye p-r-e-p-aration is the key to 
success.

As to the 2" x 4 1/4" blue welding filter: If it is glass you are ahead of 
me. I have been searching for a high quality cobalt blue welding filter for 
two years with zero success, but would love to find out more about it (HINT, 
HINT!). Remember, you are in Canada. While your safety codes are just as 
tight as in the U.S., you have a somewhat different market place.

So, why does yellow do such an outstanding job of enhancing your view? 
Certain yellow theatrical lighting gels (plastic films), while appearing 
very light, completely cut out blue light. They have the unique advantage of 
sharpening views without darkening them like red does, making these gels 
prime candidates for use in face shields during grinding and polishing 
operations. However, you must study  spectral emission graphs to find the 
right ones, because you can't judge correctly by just looking at the colors. 
Rosco, GAM, Lee, and Apollo are manufacturers of theatrical gels, and they 
all have books of color swatches with the graphs available, so start your 
search with the yellow pages (sorry, just couldn't resist).

Why give away the slickest trick in my next book? Judging by the speed of 
Gas Burners acceptance, someone more clever than me could come up with a 
mathematical formula along the lines of "the more important the information 
(I), the slower its acceptance (A), further modified by the orneriness of 
people (O); this last is a highly variable factor. I'm not sure just how the 
formula would work, but it would end up with an average result closer to the 
speed of molasses in January than the speed of light :-) I'm betting that my 
new book will be in print for at least five years before most folks even 
start considering vision enhancement! This subject is simply too important 
to sit on.
Michael Porter

----- Original Message ----- 
From: "Mike Spencer" <mspencer at tallships.ca>
To: <theforge at mailman.qth.net>
Sent: Wednesday, February 08, 2006 10:54 PM
Subject: Re: [TheForge] FW: Didymium? I say "no way."

>
>> I've done heavy research into vision enhancement for hot work over
>> the last year for one of the key chapters in my next book.
>> ...
>> Michael Porter (AKA Mikey, AKA Dr. Frankenburner)
>
> Thanks for the research and write-up!
>
> Here's a little factoid that you might address:
>
> On my only visit to a steel mill, I was loaned a pair of glasses to
> use when watching the open hearth furnace being tapped into a ladle.
> They were deep blue and the guys said that was what they all used.
> Later I happenen to get welding goggles -- the kind with a rectangular
> 2x4 pane -- in the same dark blue.  How does this (cobalt glass??) fit
> into the filtering specs for IR?  Is this shade universal in steel
> mills or just consistent with the other Edwardian technology at the
> mill I visited?
>
> I rarely use them except for fun.  They essentially cut out *all* the
> yellow.  Hot things become a stunning crimson.  If you drive with them
> on on a bright day (death wish on a dim day) all the yellow warning
> signs become almost invisible.  Grass and trees are a muddy,
> depressing red about like dried blood.
>
>
> - Mike
>
> -- 
> Michael Spencer                  Nova Scotia, Canada       .~.
>                                                           /V\
> mspencer at tallships.ca                                     /( )\
> http://home.tallships.ca/mspencer/                        ^^-^^
> _______________________________________________
> Manage membership or unsubscribe at:
> http://mailman.qth.net/mailman/listinfo/theforge
> theforge mail list group photo site is
> http://www.photoaccess.com
> Login:  blacksmithblacksmith at hotmail.com
> password:  anvil
> ___________
>
> 