I hand polished some brass with NuFinish and some paper towels. I polished one piece of brass over and over and every time the new towel had lots of black stuff on it. The brass became very shiny. I figure something in the NuFinish is turning black when it reacts with brass. It never turns green so I know it is not a reaction with ammonia. Anyone know what is going on?

Also does anyone have any long term status with NuFinish? Does the brass dull over time or does it always stay shiny?

I pour a couple cap fulls in the corn cob media in my Lyman turbo vibrator once in a while, seems to work very well, brass stays shiny.

All of my brass that I have polished with NuFinish has remained shiny for several years. As the poster above said the black stuff is the tarnish that you are removing. I get specks of black gunk on my brass occasionally, it goes away when I add mineral spirits to the media to reactivate the NuFinish.

I was in the military and we used Brasso. Brasso has ammonia. The Brasso leaves sort of a black on your cloth but it has a hint of green (normal for ammonia). NuFinish leaves jet black on your cloth every time you use it and it doesn't matter if the brass is dull or bright. NuFinish has no ammonia and there is no hint of green. Brass is made of copper and zinc. NuFinish says it is a blend of polymers that uses zinc cross-linking technology for bonding whatever that means. Maybe it is the zinc in NuFinish that turns black. Based on what I read, this chemical reaction doesn't seem to hurt the brass (at least not that much).

That's great knowing that NuFinish  will remain shiny for several years. Thanks.

Normal results. Brass is an alloy and only parts of it will turn green when oxidized. The copper oxide can create a nice verdigris or green to turquois color, but the other elements can create a black.

Artists make this green color by oxidizing copper with vinegar to create pigments. The black oxides are common from zinc and depend on what you are cleaning with.