i have forged out a cable-dagger with the help of my mentor, i still need to make the gaurd and pommel and im going to make the handle out of polished dear antler, what i am asking is what is the best acid to put on the knife to make the damascus pattern of the cable show?

Here is a process that works great and creates a high contrast on a carbon/nickel steel Damascus blade:
I stumbled across this, trying all different methods of bluing steel.
Etch first with ferric chloride for about 15 min. to bring out a 3 dimensional pattern.
Apply cold rust bluing liquid (you get this from diverse gun shops) and put the steel in your kitchen oven at the lowest temp. and a pan of water to add moisture.
after a few ours the blade comes out slightly rusty which is normal.
Scald in boiling, DESTILLED water or use steam, that will turn the rust black.
Let dry and clean the black dust off using 0000 steel wool (carding).
Wash with baking soda (neutralizing the acid)
The blade should now be uniformly dark.
After that comes the fun part that brings out the pattern.
Polish the higher nickel areas with 600 grit sandpaper which will now be exposed and bright.
The lower parts stay dark and since they are blued, they also will be more protected from rusting.
Use a buffer if you like and oil your blade.

Junker if youi still are looking at this: When you etch with any medium The steel will get a layer of black stuff on all outside areas. Now and then I remove from etch and wash it off, then I take some 1500 grit wet or dry paper and lots of watere and rub the surfacdes to remove this buildup. Then back into the etch. I do this several times until I get the look I want. I use Pcb diluted three parts water to one part etchant.
Some things you just have to do a few times and see wot you like best,,,like Thomas said above.

600 grit or finer