About process

Anodised aluminium has a crystalline micro-porous layer which is an artificially grown version of the natural process of oxidization. Anodising involves passing an electrical current through the aluminium whilst it is suspended in a bath of acid. The aluminium is the anode, lead is often used as the cathode. The layer is part of the metal, (like rust on iron), clear and in its hard version is second only to diamond in durability. The anodising process was developed in the 1930’s and was the beginning of a huge use of aluminium in industry.

The anodised aluminium developed for colouring has a ‘soft’ layer, although it is still very durable, particularly after the sealing process. A number of proprietary inks and dyes are on the market, and many other colourants can be adapted for use.

The particles of pigment are absorbed into the micro-porous layer from the ink used for printing. The parts of the metal sheet which have not been inked during printing will take up pigment from a dye bath, after printing is completed. The colour from the dye does not affect the colour applied as ink. When the colouring process is complete it is sealed by steaming or boiling. This swells the crystalline layer, closing the pores, and locking in the pigment. All surface ink is then removed and the colours left behind are part of the anodised surface. Hence it will not flake or chip like paint. It is part of the aluminium. The colours I use are also light-fast.

Once coloured, the metal cannot be heated without affecting the colours. This limits the amount of working it will take and also means it cannot be soldered, introducing design challenges not found in traditional jewellery fabrication.