I have never used a weld-cool lens but had found myself looking for them on line and in old tool supply stores, because of all the ones for sale on the forum.(200 to 300 dollars)  I found 3 lenses at a place near my house 1-brand new 1-used but in good shape and 1-well used that I picked up for a dollar each.  I tried them for the first time in my garage just messing around running 7018 but was not to impressed.  So my question is what makes them so desirable and what is the most suited process for the lenses.  Thanks.