What causes this two-toned pattern on my brass work? - Woodworking Talk - Woodworkers Forum
 
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post #1 of 14 Old 05-24-2011, 11:06 AM Thread Starter
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What causes this two-toned pattern on my brass work?

I'm refinishing painted doors and entryways in the house. Here's some door hardware that was under several coats of paint.

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Why are the ends less tarnished than the middle? Something about the screws? Or 100 years of hands rubbing any protective coating off near the knobs? (The paint came much later)

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post #2 of 14 Old 05-24-2011, 02:00 PM
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Being so uniform, I'm wondering if they were tempered to toughen up the brass.

Did you try buffing out the metal, and see what the color looks like?
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post #3 of 14 Old 05-24-2011, 03:51 PM
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I'm stumped... That's bizarre. My first thoughts were was the skin contact but they are way too uniform... Could it have been related to packaging?...

I'm guessing it's copper under the oxidation and not a lack of copper, right?...

A little mind bottling...

~tom
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post #4 of 14 Old 05-24-2011, 06:38 PM
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I think it is how they were made. They are supposed to look like that.
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post #5 of 14 Old 05-25-2011, 12:02 PM
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Very strange. What metal are they made of? The brown parts look like copper, are they made of solid copper or copperplated iron? As said above, try to buff the dark parts and see what happens. BTW how did you remove the paint? That may have caused this effect.
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post #6 of 14 Old 05-27-2011, 10:44 PM Thread Starter
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Thanks for replies,

They're magnetic, so they are plated not solid.... and Long I think you're absolutely right.... its copper not brass. My bad. To take off the paint, I started with heat and a nylon brush, then graduated to (oops) standard paint stripper. It's possible I might have damaged the plating. Or not. Hard to tell.

Anyway, here's one of them after a wipe down with vinegar-soda, then rinsing, and rubbing with vinegar-salt.

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Seems there's still some copper under the brown coloring in the middle. BTW, the back is stamped with "McKinney" and the house (Pennsylvania) was probably built in the mid 1920s.

The finish still seems kinda beat up so maybe we'll replace 'em. Then again, they are a nice heavy material, much nicer than the chinzy stuff at the BORG so we'll check out the cost to make 'em all one color again with new plating or powdercoating.

Anyone ever had that done? Please tell about it!
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post #7 of 14 Old 05-27-2011, 11:04 PM
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I'd try a buffing wheel, and some red rouge. If you polish through the copper, it can be replated. Any place that does chrome can do it, copper is used on steel before chroming.
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post #8 of 14 Old 05-28-2011, 01:45 AM
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My guess is that it's corrosion and pitting (verdigris).

Since it's brass/copper and not iron it won't show much pitting at all, but it still corrodes. The mechanism is the same, no matter what the metal.

the reason I say that is because the hinges show it as well - and they wouldn't have come into contact with hands.

That's just my guess.
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post #9 of 14 Old 05-28-2011, 03:47 AM Thread Starter
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Quote:
Originally Posted by klr650 View Post
the hinges show it as well - and they wouldn't have come into contact with hands
Good point.

Gets me back to the other question.... why the two-toned pattern? Is there some weird metalurgy thing going on with the screws that makes that area resistant?
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post #10 of 14 Old 05-28-2011, 05:54 AM
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Just a thought...try some Brasso. I'm thinking if it was some sort of metallic reaction, the shading would be more shaped to the screws. More likely what was done or applied to the surface over time, or a difference in surface exposures.








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post #11 of 14 Old 05-28-2011, 06:41 AM
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http://www.mckinneyhinge.com/catalog/kb.cfm?kb_id=460

McKinney's are a longtime,Colonial Revival hinge,favorite.Need to hang onto all the old ones you can get.We were usin them on Retro kitchens before the term became overused.

Its hard to say what the cause or why your backer plates look like that.I wouldn't be replacing them and wouldn't pwd coat either.Try to replicate the original finish.Probably a baked on,simple enamel.Which hey,it worked good for how many years?Why change?Its fairly easy to rig up a heat source,google/research the temps involved.Look at the process as a "hillbilly powder coat",haha.I'd be thinking around 120* F,or so.Spray bombs suck 'cause you're buying solvents not paint.A 27$ "Purple" HVLP gun from H.F. and some Tractor Supply enamel w/hardener should.........get you pretty close to original.BW

Those who say it cannot be done shouldn't interrupt the people doing it.
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post #12 of 14 Old 05-28-2011, 07:38 AM Thread Starter
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Thanks C,

And thanks BW! Whoa.... this site's collective brainpower is awesome. That's great info.

SteveEL
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post #13 of 14 Old 05-28-2011, 07:56 AM
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Quote:
Originally Posted by BWSmith
http://www.mckinneyhinge.com/catalog/kb.cfm?kb_id=460

McKinney's are a longtime,Colonial Revival hinge,favorite.Need to hang onto all the old ones you can get.We were usin them on Retro kitchens before the term became overused.

Its hard to say what the cause or why your backer plates look like that.I wouldn't be replacing them and wouldn't pwd coat either.Try to replicate the original finish.Probably a baked on,simple enamel.Which hey,it worked good for how many years?Why change?Its fairly easy to rig up a heat source,google/research the temps involved.Look at the process as a "hillbilly powder coat",haha.I'd be thinking around 120* F,or so.Spray bombs suck 'cause you're buying solvents not paint.A 27$ "Purple" HVLP gun from H.F. and some Tractor Supply enamel w/hardener should.........get you pretty close to original.BW
Baked enamel, makes sense. That'll change the colors of metals underneath.
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post #14 of 14 Old 06-03-2011, 08:17 AM
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thanks....
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