copper/nickel brightener

[txturbo]

What is the purpose of this additive? Does it have to be used?

[mcaswell]

If you ever need to carbon filter your solution to remove contaminants, the filtering process removes the brightenters. You will have to add more.

[48Buick]

Turbo:
The brightners and levelers in a nickel and copper bath help to smooth out the plating as the process happens.
If your working with old pitted metal, its a good idea to have brightners and levelers in the copper bath. If you do decide to use these additions, you must use a phosphorized anode instead of a oxy free anode.
For the nickel, it will give you a plating that needs no buffing whatsoever. You can simply rinse and go straight to the chrome.
Caswell is correct in that if you ever have to carbon treat your bath for organic contaminates, your brightners and levelers will be taken out and need replaced.
Through usage of the bath, you have to keep the adding these to the bath as they get used up.
Good luck!
48Buick