Woody, master of machine and coin, recently developed a new anodizing technique for our niobium moons:
- One layer of anodization covers the coin with blue.
- That layer is partially tumbled off over a few hours. This leaves the first blue layer in the lower parts of the design (shadows) and the higher parts are raw niobium again (highlights).
- The 2nd anodization puts purple onto the highlights to create the two-tone effect.
In addition to this new patina, this is the first time we've ever made a large 1.5" anodized niobium moon.
Anodization of niobium is not a plating or dyeing process, but it in fact increases the thickness of the natural oxide layer on the surface of metal parts. This layer refracts light bouncing off of it which creates the blue and purple colors you see here. In fact, these coins are really hard to photograph since the colors will change a bit depending on the angle of the light hitting the coin. Water on the coin will also change the color dramatically. The colored anodization is very durable, but will wear down over years at the same rate that niobium will wear down, mainly in the highlights.
Check out the 2nd anodization process video: