Answer: Not always.

That’s right. Tattoo ink is NOT always vegan. Tattoo ink is made from color pigments plus a liquid carrier. Some black inks are made with bone char. Some liquid carriers are made with animal by-products. Look for inks that use plant based glycerine. Below is a list of current (2012) vegan ink brands:

Classic Ink
Stable Ink

When in doubt, ask your favorite artist. Any artist worth getting tattooed from will have fairly detailed knowledge of their tools. Just ask. For more information (potentially outdated), check out the following links.

VegPress.org: Tattoo and Aftercare Information for Vegans (Fall 2011)
Jinxiboo: All About Vegan Tattoo Ink, Aftercare, and Supplies (Spring 2010)

I’d love to pull together a list of tattoo artists that use vegan inks. If you know someone, let me know. Lets see if we can create an official list.