I hope there might be someone out there who can offer a bit of advice & assistance!

I have previously had some success anodising small pieces of titanium using 9v batteries & Coca Cola (strange but true) and decided to go mad & buy some "proper" kit in the hope that it might make the process easier. I am now the proud owner of a 1amp, variable voltage (0-120) benchtop power supply, but having donned my safety rubber gloves and taken a very deep breath (all those volts + liquid is scary stuff!) I am having a few problems.

I have Grade 1, 0.5mm Ti sheet which I have prepared by degreasing in an ultrasound bath, then soaked in Titanetch, rinsed in Sodium carbonate solution & anodised using ammonium sulphate (I have tried 10 & 20% solutions) I have managed to obtain passable gold, blue & purple colours which seem to develop at much lower voltages than I expected, but I am unable to get anything approaching pink, teal or green. My understanding was that the colour is largely voltage dependant and to get the pink to green range I would have to crank the voltage up towards 100, but when I do this (incrementally) all I am getting is a lot of fizzing, sparks which look a bit like a microwace arcing and a very dull, almost lilac matt colour finish. I am using Ti wire to hold the pieces in the solution, btw.

Can anyone offer any advice? I am not sure if it is the solution I am using, my prep technique, the electrical bit, or the holding wire which is causing problems. It seems (with my limited knowledge of physics and metallurgy!) that somehow the oxide layer is preventing the colours forming? (Excuse me experts if this is a daft thing to say ;-))

Thanks in anticipation!

greneeyedleo