In this very short instructable I'll explain how easy it is to do this to your Zippo shell.
Step 1: What You Need, or What You Want
to do this project you need:
1)Enamel paint, most hobby stores will stick this and it is model paint.(you need enamel because it is oil based, make sure your paint says enamel on the sticker.) you can use the kind in the spray can found at the hardware store as well.
2) (optional) borax. I don't know exactly what it does other than soften the water but my project came out fine with out it.
3)water in a bucket(warm water is better), make sure the bucket is not special because it will get paint on it.(i used a bottom of a 2 liter bottle)
4) a Zippo(or any other random thing you want to dip.)
Step 2: Some Explaining
sorry, I did this ible' after the fact so no dipping pictures.
You spray, or drop some paint of varying colors onto the water surface and swirl it around with a stick or somthing. And then suspend your Zippo on a string and dip it into your paint on the water. Move the paint on the water away to the side of your bucket, and lift your object out of the water(as to not coat it a second time).
hang your Zippo on a tree or somthing to dry over night.
Note: I tied a string at the hinge so when I dipped mine it was open. be careful not to get to much paint inside the Zippo.
Step 3: Done!
hopefully you remembered to take the working part out and only dip the shell......... have fun showing off your marbled Zippo and let me know your opinions in comments.