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I restored antique brass door knobs and plates.

This is what the brass looked like before restoration. enter image description here

This is what the brass looked like after restoration. enter image description here

The door knobs have a color mix of yellow and copper. The plates have mostly copper color.

Which color is supposed to be the original brass? And what or where is the other colored layer from?

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  • It depends on where they were made a higher content of copper will give them red color and in some homes was normal. I haven’t done any restorations for quite a while but maintaining consistent hardware can be tough with the patina sometimes it is hard to tell but once stripped and neutralized it is best to clear coat so the colors are bright some homes are all yellow brass, and the porcelain knobs were the other common differences. – Ed Beal May 16 '20 at 18:23
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    I suspect that the darker color on the plates in the first photo was the original finish, a rubbed bronze perhaps. – Alaska Man May 16 '20 at 18:50
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Copper is "red", adding zinc to it makes it brass and the more zinc the more yellow/gold. However , there is always an exception. Yellow brass is usually 70 Cu; 30 Zn, but a cheaper yellow brass is ( muntz metal ) 60 Cu ;40 Zn and is a little reddish compared to 70;30. For these two alloys the color trend reverses. So it looks like the knobs are 70;30 and the plates are 60;40 ; both are brass.

These consumer items are very unlikely to be bronze ( Cu + tin ) which is more red than brass.

Well over 100 years ago some consumer items were bronze instead of brass. Plumbing materials are a little different as the better properties of bronze make bronze a little more likely to be used for plumbing.

Very long ago I worked at a secondary copper smelter; they melted copper alloys into standard composition ingots. It was important to separate copper scrap into about 10 categories. Experienced people could sort tons of these alloys by color and form, not counting the pure copper wire and tubing/pipe.

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  • Interesting answer. If you look very closely at the door knob that is farthest away in the second picture, it has the yellow color along the edge, and copper color on the face. You can also make out a little yellow ring inside the door plate holes. So it's a mix of color. Are you saying that different areas of these pieces have different amounts of copper and zinc which creates this color mix? – Wandering Fool May 16 '20 at 20:32
  • Some cleaning solution may have removed some zinc from a very thin surface layer cause color shading .In industrial heat exchangers ,loss of zinc can be a problem but never in a domestic application. – blacksmith37 May 17 '20 at 20:12
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The brass you now show was not the original finish otherwise the brass would be matched in color.

The original finish was japanned or painted.

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