[TheForge] Anyone own one of these? Opinions?

Wed Jan 8 17:53:04 2003

I have a Jackson Master model auto darkening helmet which has variable shade
and also settings for using it as a grinding shield or burning shield.  I
wouldn't be able to weld without it. I too cannot get the "nod" right.  I
mainly work with tig so it is very helpful.  I bought it about a year and a
half ago for $275.

The rating is supposed to 1/25,000 of a second which is probably the most
important thing to look for in a auto helmet.

Bill Futer

----- Original Message -----
From: "Bruce Freeman" <[email protected]>
To: <[email protected]>
Sent: Wednesday, January 08, 2003 5:07 PM
Subject: Re: [TheForge] Anyone own one of these? Opinions?

Chuck,

Is flash BURN really an issue here?  "Burn" implies actual damage due to UV
on the eye.  (SOME of this damage does heal, but you may be right about it
being cumulative.  I simply don't know.)  What I WOULD expect is flash
"dazzle", where the bright visible (non-UV) light dazzles you, causing your
pupils to shrink, leaving an intense after-image, and generally making it
difficult to see � but without doing permanent damage to your eyes.

I have virtually no experience with these helmets, not being a weldor
myself. (I've worn one once or twice.)   But what I DO know is that ordinary
window glass is virtually opaqe to UV.  I don't know the "% transmittance"
of glass to UV light, only that it's quite low.

(FYI, "% transmittance" is the percentage of the incident light that will
pass through a layer of glass of some standard thickness, usually 1 cm.   If
99% of the UV light is absorbed by a 1-cm glass plate, then 99.99% will be
absorbed by a 2-cm layer, but only about 40% will be absorbed by a 2-mm
glass plate.  Transmission i's highly dependent upon wavelength.  A glass
that's clear for white light can be "black" for UV light.)

Bottom line is that if your color-changing mask does pass too much UV light
in that brief interval before it darkens, then the fix would be to add an
additional filter of clear glass of sufficient thickness to filter out all
the UV, regardless of the color of the changeable filter.

Bruce
NJ

>>> [email protected] 01/08/03 04:21PM >>>
I've had several automatics, both cheap and expensive.
The cheaper units tend to take about 2X the time the best units do to
change.
The more expensive ones also tend to let more light thru the lens so you can
see your work piece in dim light conditions before you strike an arc.
If you are using the HF unit for extended welding sessions I recommend that
you
close your eye lids as you strike the arc, to insure you minimize the flash
burn.
Remember the arc damage is cumulative.
Chuck

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