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

Fri Feb 10 18:35:19 EST 2006

Chuck,
When you say filters without saying spectacles or safety glasses, my mind 
automatically registers this as belonging in the burner goggle category; in 
other words either as 1.95" rounds or as 2" x 4 1/4" rectangles or even as 
4" x 5" welding helmet filters. The only kind I know of are ANSI rated shade 
#4 and #5 gold plated plastic filters. The view through these is superior to 
standard green glass, but not what I would call impressive. I haven't heard 
of a gold plated didymium filter plate, but would be delighted to have my 
ignorance corrected.

As to spectacles or safety glasses, there are gold plated ANSI rating shade 
#5 polycarbonate lenses offered by Oberon in Didymium II Blue, Cobalt II 
Blue, Welder Series (green), and Image Orange safety glasses. I haven't 
purchased a pair yet, but will try the first three after my next royalties 
check comes in. I wear prescription glasses, so they are just research to 
me. Afterward, students can borrow them from the pile of test products. Be 
happy to hear your evaluation of them versus a standard shade #4 lens. If 
they are superior, they should at least be able to match the view from the 
next lower ANSI shade.
Mike P.

----- Original Message ----- 
From: "Chuck Robinson" <robi5515 at bellsouth.net>
To: "Sponsored by ABANA" <theforge at mailman.qth.net>
Sent: Friday, February 10, 2006 1:05 PM
Subject: Re: [TheForge] Re: Subject: Didymium? I say "no way."

> Mike,
> What is your take on the gold vacuum deposition/didymium filters? they 
> seem far more effective than any thing else I have used.
> Chuck
> ----- Original Message ----- 
> From: "Mike Porter" <michael.a.porter at comcast.net>
> To: "Sponsored by ABANA" <theforge at mailman.qth.net>
> Sent: Friday, February 10, 2006 12:52 AM
> Subject: Re: [TheForge] Re: Subject: Didymium? I say "no way."
>
>
>> Pupil? I meant to say iris.
>> Mike P.
>> ----- Original Message ----- 
>> From: "Mike Porter" <michael.a.porter at comcast.net>
>> To: "Sponsored by ABANA" <theforge at mailman.qth.net>
>> Sent: Thursday, February 09, 2006 8:53 PM
>> Subject: Re: [TheForge] Re: Subject: Didymium? I say "no way."
>>
>>
>>> Bruce,
>>> Any light in sufficient amounts will burn your eyes. It is true that the 
>>> smaller the wave lengths, the greater the amount of energy they carry. 
>>> This is why UV is more harmful than IR. However, they both have the same 
>>> main hazard--they are invisible. You don't react to either UV or IR. 
>>> There is no pupil contraction to either one of them, no blink reflex, no 
>>> urge to look away, as there is with too much visible light. This has 
>>> every bit as much to do with  physical impact as the square of the 
>>> distance.
>>>
>>> Also, only far range IR is felt as heat. Near range IR is not felt at 
>>> all, just as green light isn't felt. So, if it packs so little energy 
>>> compared to every other light band, what is the big deal? That there is 
>>> so very much of it whenever anything is heated past 1000 degrees. The 
>>> amount of energy that super heated objects put out as IR is huge before 
>>> you ever see the faintest glow of visible incandescence. As they 
>>> brighten into the visible range, the IR multiplies as well.
>>>
>>> Lots of people can't just look away from the heat source. How do you 
>>> braze or gas weld without looking at the heat source? How do you pound 
>>> incandescent hot iron without looking at it? I'm not saying everyone 
>>> should rush out and get protection from IR. That's your individual 
>>> choice. I was originally answering a question asked by someone who does 
>>> want that protection.
>>> Mike P.
>>> ----- Original Message ----- 
>>> From: "Bruce Freeman" <freemab222 at yahoo.com>
>>> To: "theforge" <theforge at mailman.qth.net>
>>> Sent: Thursday, February 09, 2006 6:45 PM
>>> Subject: [TheForge] Re: Subject: Didymium? I say "no way."
>>>
>>>
>>>> Unlike Mike, I have NOT intensely researched
>>>> protective eyewear.  However, I have one pedantic
>>>> correction to his posting, and one genearl issue.
>>>>
>>>> The pedantic correction is that the yellow "sodium
>>>> flare" has nothing to do with soda reacting with air.
>>>> Merely heating sodium to flame temperature is
>>>> sufficient to produce the flare.  Okay - who cares!?
>>>>
>>>> The other observation is what I consider an excessive
>>>> concern about IR radiation.  IR is translated to heat
>>>> when it encounters anything that absorbs it.   If that
>>>> thing then gets warm, it will retransmit IR.  Ordinary
>>>> glass absorbs most IR, and many plastics do as well.
>>>> You can tell if a lens absorbs IR:  place it in front
>>>> of a heater and see if it gets hot.  Unfortunately,
>>>> that will not tell you what wavelengths it absorbs,
>>>> should that matter.
>>>>
>>>> The thing about IR is that it is the least likely
>>>> radiation to get you in trouble -- because you can
>>>> feel it.  If you're so "manly" that you refuse to look
>>>> away from the fire as your face cooks, then your
>>>> eyeballs will cook along with your face.  Remember the
>>>> reverse-square law:  Twice the distance from the heat
>>>> is 1/4 the heat intensity.  Pretty easy to avoid too
>>>> much IR.
>>>>
>>>> None of this is to say that IR should be ignored.
>>>> But, finding a clear material that would PASS IR has
>>>> been a significant problem in science.  Ordinary salt
>>>> (NaCl) works, as do the chemically -related salts,
>>>> such as potassium bromide (KBr).  Even those start
>>>> absorbing if they pick up water, so they have to be
>>>> kept dry.
>>>>
>>>> Bottom line:  Don't be stupid and try to cook your
>>>> face and eyeballs, and you'll probably have no problem
>>>> with IR.
>>>>
>>>> UV is another ball of wax.  Never look at an arc, even
>>>> briefly.  Even the reflection of an arc can be
>>>> damaging.
>>>>
>>>> Bruce
>>>> NJ
>>>>
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>>
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