iv had my crusader cup for 2 years now, my wife got me the black one for xmas. its got to a point that im finding the black coating in my brew and its putting me off finnishing my drink.
so I have desided to take the stuff off and this is how I did it
1st heat the cup up over your stove
then take a wire spunge and wipe the stuff off
make sure you wear gloves for the inside of the cup that way you wont burn yourself
and here is the finnishing product
just thought i would share for thoughs who are planning to do this 
so I have desided to take the stuff off and this is how I did it
1st heat the cup up over your stove