The Oxidizer I sell is a one step process as always done. BUT if you have an area that is big to darken or the material is tough to keep black like aluminum. Then u use a 2 step process. First a cleaner that preps the surface. Wipe off, then oxidize as normal. Same solution works on Brass or Aluminum. 100% guarantee. Sold hundreds and have not heard a complaint. All the solutions are 100% concentrated, no cutting is done to make a sample at the show go better. But some materials will darken better than others. I just buy the std brass from Creative Metal. Leaded is too rich for my blood.
If you mix the solutions or the brushes in the 2 steps it will not work. One is designed to remove and the other darken. Not sxure what the results would be.

I can answer any questions you may have via email if u would like add'l info. fred@q1engravers.com

Fred