Whiting powder is something I use everyday to clean and finish all my stained glass pieces.  If your having a hard time with oxidazation buildup on your solder, try vinegar wipe followed up with a good cleaning using the whiting powder.  The acid brush that I'm offering is the same one I use and so far its the best brush I have found for this application.  Free Shipping in the US! Check out my Facebook page and YouTube channel for more tips and tricks!
This combo pack contains: 1 - 1lb. Bag Whiting Powder
                                                        1 - Acid Brush
Use: Clean excess flux, oil, & putty from work, also darken solder & lead