Speaking of ammonia. This is something that I have experienced in the last couple of months. I have used aqua fortis on and off for a longtime. I generally just use baking soda to neutralize and never have had a problem with "after rust" on the barrel or other parts. I purchased a new bottle of AF and added it to some that I've had for quite awhile. I finished up two rifles and put them away. I pulled one of the rifles out and to my surprise the barrel and trigger plate, screws etc. were rusty. Maybe I forgot the baking soda, I forget things, I tore the rifle down and reapplied baking soda. I checked the metal a couple of weeks later and..... rust again. I then went with ammonia and that seemed to work. My thinking is that the new AF was still cookin and I will only use ammonia in the future. Hope this saves someone from extra work.