I'll walk you through how I anodized my new titanium cyclocross bike.
Step 1: Materials
1. Rubber gloves (to avoid/prevent electrocution)
2. Plastic bowl/bucket/container
3. Small piece of sponge (1 x 1 x 1 cm), or a small piece of cloth (e.g. small strip of towel)
4. Voltage source that can be adjusted from 20-120 V. I used a commercial lab bench supply, but most people don't have these lying around the home. A good solution is to buy twelve 9 V batteries and connect them together in series. This allows you to adjust your voltage in discrete 9 V increments, or you can add a couple smaller voltage batteries in series as well.
5. Alligator clips to connect to your workpiece
6. Comet cleaner (I used this because it is cheap, i.e. less than a dollar), baking soda, TSP (trisodium phosphate), ammonium-phosphate, or Borax. Basically, anything similar to these products. Coca Cola or Pepsi will also work.
We'll be using some simple chemistry and electricity to perform magic!
Step 2: Get Things Ready
Pour in about a tablespoon of your cleaning powder.
Stir/shake it up a bit.
Put your rubber gloves on so you don't electrocute yourself.
Step 3: Electricity
Important note: once you go up in voltage and add another color (e.g. pink over blue), you can't go back to a color at a lower voltage.
However: The anodized layer (an oxide layer, I think) is pretty thin, too, so if you screw up or don't like it down the road, you can put some elbow grease into it and buff it out. Using scotchbrite, high grit sandpaper, or similar will brush/polish your titanium right up. What an amazing element.
Connect your alligator clips to the positive and negative terminals of your power supply or battery array.
Step 4: Apply the Magic
Grab the small piece of sponge with the negative electrode. Try to make sort of a paint brush with it.
You may chose to take a precautionary measure and wrap tape around the alligator clip and sponge such that you won't short out your power supply on the titanium.
Or ditch the sponge and use a piece of cloth.
The object here is to have something that will hold a bit of the water/electrolytic solution that will be "painted" on the titanium.
Step 5: Mask and Paint
You may also choose to clean your titanium to remove fingerprints, dirt, etc.
Find an inconspicuous spot on your piece of titanium to test your color. Start with a lower voltage and increase it until you get the color you desire. REMEMBER: you can not get a color at a lower voltage once you've applied a color with a high voltage (e.g. once you get pink at 85 V, you can't get blue at 35 V)
"Paint" your titanium!
I noticed the colors at the lower voltages seem more stable and consistent. You can see in the pictures that the blue is a nice, consistent, smooth color whereas the pink has a yellow hue to it (yellow comes just before pink when anodizing Ti) and is very splotchy (probably because I didn't clean the frame very well, and because the same voltage wasn't getting to the whole surface evenly).
Step 6: Marvel and Awe and Make Your Friends Jealous
"I love you?
edit: seriously though that's cool as two dogs " - Nick!
"Whoah, that does look real nice though. " - DonPenguino
"That looks amazing man." - Mr. Panda
"That is really cool!" - sage
"I'm gonna cry, that's beautiful. " - Charlie Short