Hydroforming vase maquette 

I was also wondering this.

I use the valve to bleed out any air, I tighten it when there is just water coming out. I wouldn't be able to fill the vessel if I didn't so this any presence of significant air could result in the piece exploding due to airs compressibility

@@luciantaylor9238 Awesome, thanks! I had assumed the valve was on the fluid in, not the line out. Makes much more sense now.