Once in a while I have my son, or various visitors, see welding arcs, from some distance such as 10 feet. I give them a regular (not automatic) helmet and the standard shades are just too dark. The question is, is there any possible risk in using much lighter shades, like 4 or 2? It seems that it should be safe,a s the helmet has UV protection built into its regular glass cover. Right?
I don't think there is any risk because they will all block enough of the dangerous UV to make it safe (assuming it's a real welding shield and not sunglasses you are talking about). But still, if it's a kid, you just have to worry. I wouldn't advise that he make it a habit to spend hours watching you weld with a light shade helmet but now and again it should be ok. You have to watch out for reflected light coming in from the back and sides as well and depending on the helmet they are using and how reflective your shop environment is so that might add up to an issue for young eyes that still have a life time of abuse to survive.
Let met pass on this story I heard. I have no idea how true it is (or how accurate my telling of it is). My previous (now dead) welding instructor told us he had a welder friend that did an all day welding job inside a store with a large front glass window. Someone across the street in an office (behind yet more glass) spend the whole day watching the pretty light from the welder because from that distance, it wasn't too bright to watch without a shield. This was a story about how a welder is always responsible for shielding the public from his welding arc and how this one guy didn't put up any type of shield because he thought he was safe inside the store. The guy across the street ended up having permanent damage to his eyes (which of course didn't start to show up until later), and the welder was sued and lost his welding business as a result of the error.
The idea of course is that people are fascinated by the bright lights and find it hard not to look. And of course, most people don't realize how dangerous it can be. So just because they want to watch, doesn't really mean you should let them do it too much even if you have the right shields for them. I would be worried about finding my kid watching me for 15 minutes with some fake cheap sunglasses before I even realized he was there (I'm that dense at times when I get engrossed in my projects). I'm sure you are better than I am about such things. :)
#5 is fine for 10 feet distant as long as you don't stare for prolonged periods.
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