[TheForge] Anyone own one of these? Opinions?

Wed Jan 8 17:11:00 2003

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 =AF 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. =20

(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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