its been ages since I researched it, I pieced it together from various sights but most of it escapes me now.
me and another member (happy chris) had a go at the standard anodising, he was over the moon with it, I'm surprised he didn't try anodising the dog :)

I think (if may memory serves) for hard anodising you need to keep the temperature at 5*c or lower which is a tad difficult if your hammering it with a higher voltage (30v ish?)
I was after making ball sockets 50mm diameter, my thinking was to keep the bath very small, just big enough to fit the ball in and the liquid butane would cool the ball and the ball would in turn cool the acid
you could do with a none flammable to cool it but i'm not sure what?
or maybe have a closed (ish) system that exhausts the expanded gas outside?
or do some magic with an old fridge :)