Owner uses a No. 5 for gas welding. Small things done with the MIG he uses a No. 10. For full bore AC welding he uses a No. 11.
The AC welder is VERY bright. Owner says "lots of flash." He has a curtain he uses around his welding area so I can't see it.
On one of his jobs as an engineer, he was in a shop where someone else was welding - and they had the yellow hanging shields, but he was situated where he could see the reflection "off the walls" - for the entire day. He says he got a headache from that.
The next day he wore the No. 5 glasses to work.
Dobbin