http://www.hometalk.com/482772/q-i-have-a-black-granite-composite-sink-and-there-is-a-white-film-all-over-it-that-i, http://www.hometalk.com/6052674/q-hard-water-stains-in-granite-sink

Coke and cooking foil

Not exactly a natural solution, but I have the same kind of sink and I have used Kaboom bathroom cleaner on it when it looks like that. It work just ok. Then I tried Lysol toilet cleaner for rust and lime. Took a damp cloth, poured some of the Olson on it and coated the sink with it. Left it on for 5 to 10 minutes and rinsed the sink. My sink looked brand new when dried.

Clean well with any cleaner. Dry. Then lightly rub thin coat of lemon oil over entire area. Don't use sink for several hours afterward. Will look as good as the day it was installed.

Honey, replace your sink.

I'm sorry, that was supposed to be Lysol ...

A little oil will make it look like new - lemon oil, mineral oil, baby oil, olive oil...almost any kind of oil

I clean my composite sinks with Clorox GEL cleaner. Spray on, let set 5 minutes or more if heavily stained, rinse well and dry sink before using again. Have had composite sinks for 2 years and this has worked well for me.

Use baking soda mixed with mineral oil and scrub with a scotch brite sponge. Wipe with paper towel then rinse , repeat as needed. Then go over the sink with just mineral oil and wipe any excess with paper towels. Works like a charm and this is what our installer and the manufacturer recommended.

Use mineral oil

i have a white composite ( 8 yrs old) and i use those white mr clean sponges after the regular cleaning and it takes it to a new level. then i top it off with the oil

If the cleaners mentioned don't work, 320 to 600 grit wet-dry sand paper used with water will abrade away the stain and leave a smooth finish. I used to install these sinks for a living.

I clean mine with granite cleaner that cleans and shines, if that does not bring back your shine, after cleaning well put olive oil or coconut oil on cloth and wipe sink doown well, will recondition and shine.

I sprinkled dry baking power onto the dry sink surface. Then I put hydrogen peroxide on a sponge making it pretty wet. Then started working the peroxide into the soda. Once the soda was all reacting to the peroxide I spread out an even layer over the bottom of the sink and up as high as it needed to be. Let it dry. Again wet the sponge with peroxide and rubbed until it looked the way it should (not long at all) and rinsed well. Not much elbow grease required!

Have you tried barkeeper's friend ?

I use the magic eraser too....it works great!

I have a double black composite sink and have tried several of the comments. It's more like scratches. Can these be resurfaced with boat marine paint?

These sinks are a mixture of Acrylic (like Corian) and Stone "Dust" and don't easily stain but have a "grain" to them that collects minerals. If you don't have a water softener, it's probably calcium deposits. Vinegar or CLR might be in order to dissolve out the minerals. As mentioned, a Magic Eraser type sponge does pretty well, but you still need to get down into the grain of the sink. Using lots of elbow grease and polishing the sink surface with Granite or Marble Polishing Compound will smooth the surface to reduce the roughness of the grain and reduce the ability of minerals to "stick" in the microscopic crevices. Good luck... let us know what you do.

CLR is a good Idea but I have used Bartenders friend in so many ways it may help too. You can find it in lots of stores but I would use the powder in a small spot and check any kind of product out before using it all over. Hope this helps Teresa

WD-40 works great. I have a black composit granite sink too and this is what I do.

Manufacturers told us to dissolve a dishwasher tablet in it.

I have the same issue. We had to use CLR/Lime-Away, followed by scrubbing with Ajax. We had to repeat that process about 4 times. When we got it cleaned up, I made a spray of 3 parts water/1 part white vinegar/1 tsp dishwashing liquid. We spray the sink after every use to keep the mineral deposits at bay (and, yes, we have a water softener!) .

I was recently told that a Mr Clean magic eraser did the trick.

Try filling the sink with very hot to boiling water. Add some Oxiclean laundry detergent and let it stand for 3 hrs.

I use to use "magic eraser" on ours...until we moved & now I have porcelain & use it on that too!

We have had our sink for about 7 years. We have no water softener either and don't have much of a problem. I try to make sure I clean the sink each night after use and use a sponge to wipe it clean. I will use a scrubby pad with dish detergent and rinse then use a sponge to dry the surface about once weekly.

If it is mineral deposits use vinegar or lemon juice. I read you are NOT supposed to use Comet/Ajax on these sinks. We have heavily mineralized water where I live and I use vinegar or lemon juice to clean all of that build up. Sometimes it takes several soakings before it comes off.

Bar keepers cleanser

3 drops of dawn dish detergent,1/2 a cup of vinegar, 1/2 a cup of borax. Mix in a spray bottle shake well stay and scrubber with a sos soap pad and repeat till gone. May take several times depending on how bad the build up.

Try using baby oil to bring the shine back after cleaning it with a magic eraser.

Using a magic eraser is like using a fine sandpaper, so be very careful...unless in a few years you plan on replacing whatever it is you use it on.

I would fill your sink with hot water from the tap add1/2 cup Javax a bit of dish soap,let soak till water is cool.Works for me.

Someone just told me that Dawn is not good in these types of sinks. I was surprised to hear this has anyone else heard this?