i have noticed that sometimes welders hold a guard in their free hand whilst using a torch - isn't this inconvenient?- there must be a particular reason for this as surely lt it would be far easier to have the guard secured on their head?
If by guard, you are referring to the welder's helmet, the craftsman will often hold the helmet in their hand rather than putting it on if the weld they are making is of short duration. The helmet, even the auto-ventilated ones, can be heavy, hot and tiring to wear.
It can be quite inconvenient to have a welding mask secured to your head if you're welding in short bursts or need to make constant adjustments while welding as you can't see through the mask normally. Some techniques require the use of both hands, so a head mounted mask is essential.
yes there solar operated so the light from the arc activates the lens darkener and keeps the system charged. but in many situations it's still more convenient to use a handheld to see with your naked eye, rather than to look through the small square in the sheild.