Anodising

It's a bit chaotic, but this is how the workshop looks when anodising is in progress...

 The focus of most of my current work is contemporary jewellery, made from aluminium and anodised in my workshop. The anodising process adds a hard, oxide-resistant layer to the aluminium, and also allows you to colour it afterwards, with special dyes. The process itself is relatively simple, but there is a lot that can go wrong, and there are a few key things to keep in mind. 

The anodising tank, with the red wire attached to the tank bar and the black wire attached to the lead sheet

Anodising takes place in a bath of Sulphuric acid, which acts as an electrolyte. An electrical current is run through the pieces, which are jigged and suspended in the bath on a tank bar. The tank bar, jig and pieces all need to be made from aluminium, and they are attached to the positive lead on the power supply. They are now the anode. Some lead sheet is supsended in the bath, and is attached to the negative side of the power supply. This is the cathode.

Anodising bench, with power supply

 After anodising comes dying, which is the fun part, and sealing. The dye needs to be heated in order to take properly, and then the piece is sealed in a scary green chemical, at boiling point. Even if you don't dye the piece, you still need to seal it. This closes the pores on the surface of the aluminium, and completes the anodising process.