This is a late 1800's door knob set I restored ,before and after photo. The rust comes from the iron lock set and the square rod that connects both handles .Those disintegrated and had to be replaced .The rest was made of brass and was still in good enough shape to save , except it was very hard and brittle ( almost as hard as steel ).The rest of what looks like rust is carbon from a fire and other mineral deposits .These deposits were as hard as granite .Think of trying to file a piece of granite ,it has no effect .Therefore I had to use electrolysis ( electrical erosion ) I made the electrolysis device out of stuff laying around ( some used batteries , a few pieces of wire ,a spoon, a milk jug and salt water )This electrolysis caused some copper plating which you can see in the finished photo ( middle reddish area )The rest of what I did is hard to describe :-)It involved mostly vices and hand made forms. There's also a mystery behind this piece. After I had determined the age I speculated on the background of this knob set. I guessed that there was a fire in a Victorian house built sometime in the late 1890's .I spoke about finding more from this site so my cousin set off and came back with some broken porcelain pieces .They only had 2 small corners of a hallmark on them but I searched and determined them to be from the same time same style etc.. as the knob set .I did another search through records and found a person had built a "house ?" I say "house ?" because that is how it is listed in the city records ( very strange ) This is in a location that was always industrial since the beginning of Tacoma history .It gave a name of the person who built it but I can find no other record of this person. The "house ?" must have caught fire not long after being built. This is a great mystery because anyone building a house of that stature in those days had to be a public figure ( lumber barren , railroad barren or politician etc..