It looks to me like your sink was pre-patinaed and then lacquered to preserve that look. Is that right?

If so, you have to decide if you are willing to go down to raw copper, and then live with the advantages and disadvantages of a living finish of raw copper.

If I am wrong, and your sink has no lacquer finish, you just have to clean up the stain. I little Barkeeper's Friend would be my first choice to scrub that area down.

It looks like an inexpensive Mexican or Chinese sink.

The copper underneath is unlikely to be close to pure.

It is probably recycled and has other metals in it.

If you remove the artificial patina it is unlikely to look good, at least not like pure virgin copper.

That is why they hammer and put artificial patina on the sink in the first place.

Yes it is from Mexico. Not sure about any warranty on it thought.

Does this have a protective coating on it? Does the documentation say anything about not placing hot items in the sink?

All you can do is to contact them immediately with a photo. I would not want a replacement though as I wouldn't trust their products and one plumbing cost would be enough.

Have you tried copper cleaner on it? They make creams and powders. The first time I used my copper pots, I was appalled at how dark and splotchy the bottoms looked - but then I used a copper cleaner on them and they returned to their original color and shine.

This post was edited by weissman on Fri, Aug 9, 13 at 15:26

If you put a little lemon juice on the sink and let it sit for awhile, then rinse away. What did that do to the finish? If it the sink has a natural patina, you will likely see a brighter copper color. If it is a lacquered finish, you probably will not see a change.

Our copper farmhouse sink has a natural patina, so at times where the patina gets stripped away, like from something acidic, the patina will return after a few weeks. That's why they call it a "living finish".

If your sink has a lacquered finish, I'm not sure how you'd rectify that other than trying to strip all of the lacquer to get down to bare metal. But, if the metal is as deeageaux indicates, then you'd be left with replacing the sink.

Is this an under mount or farmhouse sink?

Thanks for the advice - I will try copper cleaner.
I contacted the company and haven't heard back yet.
Yes, it's an undermount farmhouse sink. We just finished kitchen recently
and started using it. I have noticed little stains and lightening of copper on occasion and it does appear to fade back with a little time.

Mix together salt and vinegar and rub it on the heat tint with a paper towel sink and see if it removes the oxidation. That is homemade "copper cleaner" -- what I have always used to clean my copper cookware. You don't need to buy a special product.

If the sink isn't coated it will create a shiny spot and you can then clean the rest of the sink to shiny and let it repatina naturally. However, copper oxide is not good to ingest. Sink grid is a good idea.

This post was edited by rococogurl on Fri, Aug 9, 13 at 20:29

Ketchup cleans copper too, makes it shiny. Hope you can get the discoloration.

Looks like heat tarnish to me...I grew up cooking with my mom's Revere copper-bottomed saucepans and your tarnish looks just like the bottom of those pots. Wouldn't be worrying about it. Any copper cleaner & a bit of elbow grease will clean it...but you're going to have shiny raw copper for a minute or two/ day or two. But that's the nature of copper so best to get used to it! :-)

The thing about copper is that even if the sink was pre-patina-ed and lacquered, eventually or sooner, that lacquer layer is going to wear off and the copper will respond to anything that it's reactive to...acids, bleach, ammonia, etc. anyway.

Here is a link that might be useful: Creating Patina Copper/ Brass