Welding Lens

[Ron Hicks]

Stand by a lamp or work light - Put your hand over your closed eyes and remove it while your eyes are closed.
Notice Anything

It might be hard to GET-R DONE when you go blind

[Dodge]

Speaking from experience, flash burn to the eyes is about as pleasant as getting a hand full of sand poured in you eyes! And, yes, you can get flashed with your eyes closed. Plus, you get the added sensation of having your eyelids severely burned. The only comfortable position was closed for a couple days. I was young and foolish, but I learned fast; Use the proper equipment!

[Glenn]

I have been reading about the auto-darkening hoods.

There is a auto-darkening hood that claims to be the "Fastest switching speed in the world 1/25,000 of a second".

Someone please check my figures so they can be corrected if needed.

Light travels at 186,000 miles per second, (299,792,458 m/s for the metric part of the world). In 1/25,000 of a second the light will travel 7.44 miles. (speed of light divided by the time).

If we are 2 feet from the arc that means the light from the arc is 7.439621 MILES past the eye when the auto-darkening lens switches to dark. (7.44 miles x 5280 feet per mile = 39,283.2 feet. 39283.2 - the 2 feet from the eye to the arc = 39281.2 feet the light is past the eye. Divide by 5280 to convert back to miles and you get 7.439621 miles.)

Let us go at this from another direction.
Light travels at 186,000 miles per second and we want the auto-darkening feature to switch to dark within 1 foot from the arc. 186,000 times 5280 = 982080000 feet the light travels in one second. So the auto-darkening would have to switch in 1/982,080,000 of a second to protect the eye one foot from the arc.

Either way it would seem the eye is going to get a flash of arc light, at least 1/25,000 second of flash. The question now becomes is the welder person able to see the "short duration" flash?

Does the eye react to the short duration flash of light (that may or may not be seen) and is it damaged in some way? Welders do not get flashed only one time a day, but each time they strike an arc. Is the repeated short duration flashing of arc light into the eye have an accumulated damaging effect on the eye?

When you run the numbers it brings up some interesting questions.

Am I on the right track or am I chasing a gnat in order to get the hide and tallow?

[Ten Hammers]

Glenn, I have no specific answers to your questions. I use an automatic at home ( Huntsman small screen solar ) and large screen battery at work. I sometimes make couple thousand welds in one day ( at work ). I have no ill issues yet. Worst burns I have had are with plasma and no shades. I now use shade 5 ( shades not helmet ) for the plasma and get along fine. YMMV.

[Marc]

Glenn, you've done some wonderful math, but kind of missed the point. The 1/25000th of a second, or 40 microseconds, isn't to switch off the lens before the light hits you, it's to limit the amount of flash. And you missed a small point. It doesn't matter how far away the arc is, the sensor is about a 1/2-inch closer to the arc than your eye. It can't switch to dark until the light hits it.

The damage is done by a prolonged exposure to UV. 1/25,000th of a second a few times, or even a 100 times per day should not cause problems. Even if you started the arc 2000 times a day, that would be a total of 1/12 of a second exposure. That's 80 milliseconds. You probably get lots more every time you walk outside and look up at the beautiful blue sky.

Furthermore, all welding lenses block most of the UV with or without the auto-darkening. So that flash is mostly an annoyance. Limiting it to 40 microseconds keeps your pupils from contracting and lets you see better early in the weld.

[Marc]

And here's an interesting website on the topic:
A Look at Auto-Darkening Welding Helmets, Eye Protection

[RegionalChaos]

There are certain LEDs, I think the green ones, that can be seen through a normal welding lens. So if you make yourself a simple led flash light, you don't have to be blind when the 15$ hood is down.

Someone once told me "... a green 23W CFL (candle equivalent to a 90W
incandescent light), mounted on a swing arm so that you can aim it conveniently,
is a LOT less money and a lot more effective for bench work. ..."

[Dodge]

I don't weld for a living anymore, but I did used an auto helmet for several years before I quit. I also use one at home. Niether the work helmet of the home one were of the highest quality. Mine was just under 100 bucks 5 years ago. So far, I have not suffered any ill affect from the flash