Homebrew PCBs

I have been off the group for a while and I'm sure this was covered.  
In the direction for making etchant from Hydrogen Peroxide and Muratic 
Acid, it says that you can regenerate with a bubbler.  How long does 
this take?  I know it will depend on the amount and the area that was 
etched, but is there a rule of thumb to make it work. I do have to day 
that I make a small bathch and it worked great on a sample board.

John Whitney
Wis X 1/9