[Patrick] met someone, and then some stuff happened. Good for him. Because of this, [Patrick] found himself in need of a pair of engagement rings. With a friend, some titanium bar stock, and an awesome lathe, he turned out a few awesome rings and also managed to selectively anodize them with a subtle rainbow of colors.
Making a ring on a lathe is a relatively simple ordeal, but the two larger rings [Patrick] made (one was for a friend) featured some interesting patterns that aren’t easy to make without a good CNC setup. Luckily, this friend has an awesome CNC with a rotary fourth axis.
With the machining out of the way, [Patrick] then turned to anodization. This was done by constructing a simple power supply with a variac, four diodes, and a big honkin’ cap. He managed to get a good result with a sodium carbonate solution. He doesn’t have any good pictures of it, but by varying the voltage from 20 to 100 Volts, the color of the anodization will change from green, purple, to yellow, to blue.