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Copper sink clarification

Posted by aliris19 (My Page) on
Mon, Feb 4, 13 at 19:13

Can someone tell me if I have this right please?

Copper is a shiny "coppery" color. With time it oxidizes. This state is not permanent and acid or other reactions will return the metal to the shiny state, sometimes not evenly.

The evenness of the oxidized state can be maintained by oxidizing, or "burnishing" (is that the meaning of "burnish" in this context?) the metal, and then sealing it 'in place'. As long as the sealant is in place preventing oxygen from further oxidizing the metal, the color will remain at the stage it was in when "burnished". The sealant can and will scratch or degrade with time, leaving the metal vulnerable again to return of the 'shiny-ness'.

So when people market sinks with different 'patinas', that means they have sealed in a particular look from within the course of oxidation. Should that sealant wear away the patina would be gone -- that is, there is nothing inherent about a certain patina given to a sink -- it's not like, say, paint (OK, which also wears away, but still)...

Now -- those sealants, there are different kinds, right? There seems, for example, to be a "wax" but also other products -- are they all doing essentially the same thing, halting the oxidation process at a given stage? Or do these impart different qualities; does one care what the sink has been sealed with?

Finally, is this correct?: Because nothing is happening to the metal to change it inherently, one could try a sink unsealed for a while and see if it was OK, but if not, then go through the process of burnishing and sealing it later on -- nothing would be lost by not doing this right away.

Am I close please?

Thanks, wise ones!

Here is a link that might be useful: fyi, the sink I'm interested in...

Follow-Up Postings:

RE: Copper sink clarification

I think you have it mostly right, but I have a few quibbles with what you say.

To me, "burnish" has nothing to do with sealing or oxidizing. To burnish is to rub, with the intent of polishing. (Like in the metaphoric "He tried to burnish his credentials before his annual review.") So, no, burnishing is not oxidizing, it is polishing.

Yes, you can always strip the oxide off of your copper. This will turn it a bright salmon-to-"copper" color. However, it may not be shiny in one sense of that word. If the surface of the metal is rough, it will not reflect like a mirror. In fact, if you take a bright, smooth, shiny, polished, unoxidized piece of copper, and let it oxidize, then strip the oxide off with an acid, you probably will not have a smooth, reflective surface any longer. (Of course, you can always polish it again to make it smooth and shiny.)

Yes, if you seal the patina, you stop the oxidation at its current state.

Yes, the particular patina is not inherent to the sink, but rather is a function of the different chemicals it has been exposed to. (Oxidation is one reaction, but copper can react with other elements, such as sulfur and chlorine, to form other colors of patina.)

Yes, all sealers work by halting these reactions. But they have different properties, i.e., could be like a wax or could be like a varnish.

Yes, you can always "start over."

RE: Copper sink clarification

Thanks, Angie!

So.... how do I know if I want the wax they sell with this sink? Seems to me you can just let the sink accumulate its natural coloring through time and if it happens to lose it here or there, oh well ... life's long and I'm fine, I think, with letting it accumulate anew. That's just me but I gather at least some on this forum agree with it. What I can't tell is if this is a super-weird GW-attitude or just - ahem - a relatively enlightened one. ;)

So how do I know whether to buy their wax which presumably you apply once you achieve the state of patina you like? It doesn't seem to me like I would need or want this at all -- is it OK to just skip the waxing altogether then? (Will I be sorry?)

And also, one more terms-question: so burnishing is like polishing -- do you then burnish until you achieve the patina you like, then seal it? Is that the game plan for some at least?

RE: Copper sink clarification

I wouldn't mess with the waxing at all. Let it do its organic color thing and if you lose a little patina, it'll 'grow' back.

My sink from Rachiele is un-whatevered inside and is what they call a 'living finish'. Now, on the apron I had them do a color patina and that is sealed, but it's on the outside so it's fine there. They sealed it and I don't have to do anything to it, ever.

This is mine and this is how it came to me. As I said, the inside is unsealed.

 photo bestcopperapronsink.jpg

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