Addition of small amounts of hydrogen creates a reducing atmosphere i.e. improves shielding quality with respect to oxidation. Also results in higher arc voltage as does helium so as said hotter arc and higher travel speeds. Neither are cheap, hydrogen mixes are limited to stainless and nickel alloys only i think due to hydrogen porosity as said.
The weave pattern in those pics is from 'walking the cup'. The ceramic is rested on the work and the torch moved along kinda like how you'd 'walk' a large heavy barrel in that it's rolled slightly one way and then t'other. Several threads on the subject floating around the forum this one has a few vids in it. Technique is of limited use in that you need more room to be able to walk the cup, weaves and thin material don't really go together and soft materials like ally will be badly marred by the ceramic.
The weave pattern in those pics is from 'walking the cup'. The ceramic is rested on the work and the torch moved along kinda like how you'd 'walk' a large heavy barrel in that it's rolled slightly one way and then t'other. Several threads on the subject floating around the forum this one has a few vids in it. Technique is of limited use in that you need more room to be able to walk the cup, weaves and thin material don't really go together and soft materials like ally will be badly marred by the ceramic.