polident? (totally never tried it .... so don't without testing first)

Be careful what you are using to clean your sink. Baking soda should take off the metal marks from pans and the like. I keep a little container of it under the sink. Wet your finger, dip it into the baking soda and lightly scrub the mark. It should come off easily. You can also take out stains by doing the same thing, but just leave it on the stain for awhile. If it is a really tough or old stain, try Barkeeper's Friend, but again only scrub lightly. Neither of these are as abrasive as kitchen cleanser and will keep your sink from losing it's finish. My porcelain sink is over 17 years old and still looks pretty new. You might want to invest in sink mats as well. It does help save your sink from scratches and marks, both porcelain and stainless.

Once you wear away the finish, it's gone. It cannot be restored. You will have to replace the sink. Get a grid if you're getting metal marks. And stop scrubbing with abrasives! A green scotchbrite scrubbie should be enough to remove anything from the sink's surface without damaging it.

Going forward (perhaps with a new sink), you might use a product I learned about on Gardenweb: R.O.G.1, one of the only cleaning products recommended by Kohler for use on their cast iron tubs. It works great on the cast iron tub and sink. It leaves a beautiful shine.

I think once the glossy finish is gone, it is gone. I had a small patch that was worn down and tried gel gloss which I heard of here. Absolutely worthless.

Here is a fascinating blog article about products to use on Kohler sinks and tubs.

http://retrorenovation.com/2012/11/19/kohler-says-no-to-magic-eraser-comet-bar-keepers-friend-zud-vinegar-for-cleaning-its-porcelain-enamel-cast-iron/

Thanks for your help

All I have been using is lysol (non-abrasize and bleach free) and a scotch-brite pad, so I am surprised to be wearing away the gloss!

Are you sure that you have a cast iron sink? Acrylic sinks look similar, and American Standard's Americast also looks similer. They are NOT the same.

I have found Bar Keepers Friend works great on my Porcelain sink. I have a 15 year old Kohler sink and Bar Keepers Friend removes scratches and food stains much better than softscrub. I have read that procelain sinks can be waxed. Havent tried that yet.

It is definitely porcelain on cast iron. I know because I bought and installed it myself. I added the link to then sink. I have never seen barkeepers friend here in Atlantic Canada.... I will have look around

Here is a link that might be useful: sink

Hmmmm....never heard of that maker..only a 5 year warranty. (Kohler is a lifetime) I do hope it holds up for you, but I'd bet it's Chinese in origin. It has all of the hallmarks. That, coupled with your report of it already wearing down doesn't bode that well.

I love that sink. I almost bought it myself, but I was afraid to veer off of the Kohler reservation. Did you buy it from Signature Hardware? If so, give them a call. I have found them to be pretty good with service issues.

Back to your problem: at this point, why not try waxing the sink? Can't hurt.

I talked to signature hardware and they said that often times people think they are wearing off the glossy surface but it is just soap scum. They recommended soaking it with hotwater and vinegar. At first I thought it didn't work but if I rubbed really hard with my finger afterward it seems to rub something off the bottom (hopefully that wasn't skin off my finger instead)!

I will continue to investigate

Marcolo, Any recommendations on a product to wax it?

I found some barkeepers friend at a local store, but they only sell the powder, not the cream. If I try it I will likely rub very lightly so as to not cause any damage (if it is infact soap scum and not finish damage).

Signature hardware has a 5 years warrenty on the finnish if I could only find my receipt! I know it didn't come in the crate so it would be in my work email acount.... no luck finding it yet!

There is a post on retrorenovation.com about cleaning Kohler cast iron sinks. Opinion about Barkeepers Friend is very strongly both for and against. There's some weird cleaner called ROG that Pam says works well. You might want to Google it and check it out.

I checked the Kohler website and they have a wide array of products that they recommend including barkeepers friend. Apparently Kohler makes a cast iron cleaner that also removes pot marks.

I am sorry. What is rubbing compound?

https://www.walmart.com/ip/Turtle-Wax-Renew-Rubbing-Compound/16888958

There's some weird cleaner called ROG that Pam says works well.

It works great, but it's meant for tubs, not kitchen sinks, and it's very expensive. It's a great cleaner of last resort for a tub that's so stained it's ante up for ROG or pull the tub, but it's full of stuff I would not use around food.

ETA It will not restore a bad finish, just improve the looks of what's there.

Hello htracey. Are you still having the same issue? I bought a clawfoot tub from Signature Hardware and a farmhouse sink as well. The bathtub has been installed only since 2013, and I have weird etchings and marks in it where it appears that the enamel on the porcelain has been worn away. It can't be from scrubbing because they are not even at all, and in fact some of the spots with missing enamel appear to be circular and where I had placed a non-slip mat. I'm really nervous because I have already found a dull spot on the sink - which has only been in use for a few months. :-( Did you ever figure it out? I contacted Signature Hardware, and they blamed it on water quality and refused to honor their lifetime warranty.

Le Creuset is also enamel on cast iron and they recommend wiping with vinegar to restore the shine. Results are mixed, but worth a try.