Resist pen.

[jdm61]

A while back, someone mentioned that a certain type of pen/magic marker works really well as a resist when etching damascus. anyone have any idea which one that might be?

 

[Jason Fry]

I've used a regular black sharpie with ferric chloride before to etch a simple logo.

 

[Stacy E. Apelt - Bladesmith]

If you buy a circuit board etching kit, all they send you is a bottle of FC and a Sharpie marker.
Any permanent marker seems to work, but Sharpies seem best.