As you may see, we have many different colors for the titanium chopsticks, it is very magic and is also one of the advantages of titanium. The process is as following:
Anodizing Titanium is easy. All you need is a 3 to 110 volt DC power supply (I usually work in the 30 to 60 volt range), some salt water (I use ammonium sulphate) and a brush with a plastic handle and a metal ferrule retaining the bristles. By varying the voltage and/or repeatedly going over the same section a wide variety of colors can be had. If you try to do the whole tube in one bath you’ll need a good deal of current (10 amps per square foot). A brush worth at a time can be done with D cells.
The following table is excerpt from “Jewelry Concepts and Technology” by Oppi Untracht.
Color Voltage Film Thickness in microns
Pale Yellow 3-5 0.0300
Straw Gold 10 0.0350
Dark Brown Gold 15 0.0400
Purple 20 0.0460
Blue Purple 25 0.0527
Deep Blue 30 0.0600
Medium Blue 35 0.0630
Pale Blue 40 0.0658
Blue Green 45 0.0700
Green Blue 50 0.0825
Pale Green 55 0.0950
Green Gold 60 0.1075
Rose Gold 70 0.1300
Red Purple 75 0.1400
Purple Gold 80 0.1500
Dull Purple 85 0.1600
A thick coating is more resilient than a thin one, but I find that thickness over 0.1um produce colors that are too muddy for my tastes.
Also, there’s no need for the DC supply to be well filtered. Unfiltered rectified AC will work. My “painting” unit uses a variac to feed a full wave rectifier and subsequently 2000 uF of capacitance. There’s a meg of resistance across the cap to bleed off residual charge when the power is off. Exactly why that’s there I’ll be keeping to myself.