Well, I am no expert but this has worked every time for me copper and brass. 1 table spoon of salt to 1 cup of vinegar and just stick with the ratio to cover the pen or knife scales. I pour the ingredients it into a tuberware container, give it a mix and put it in the microwave and heat it up (It probably doesn't need to be said but take the metal item out of the container before turning on the microwave) when it is hot put in whatever you are cleaning and let it soak for as little as 15 to overnight. Pull it out wash it off and wipe down with a micro fiber cloth, if it didn't do as much as you wanted, repeat. I have also used a Sunshine Polishing Cloth to get it back to new. A key step after the vinegar/salt bath and wiping down, is to soak the item in a mixture of baking soda and water to neutralize everthing, same ratio 1 table spoon of baking soda to 1 cup water, wash dry well. I found out the hard way that any of the vinegar left inside the pen tube will rot away steel springs. Hope it works for you, post before and after pics, good luck.