Interestingly enough, copper is more sanitary than most other basin materials and is actually "antibacterial". Science shows that bacteria can live for days on a stainless steel surface, but for couple of hours on copper.
Copper sinks: made from the highest quality copper available. Patinas on these sinks are created by a firing process and will change over time. Caring for copper sink is easy and virtually maintenance free. A copper finish is a living finish and is constantly, gradually changing in color. You can reduce this change with the use of a Copper Patina Repair Kit (purchase at YK Stone Center $56.99)- An easy kit designed to touch up or change the finish patina on copper sinks.
For basic cleaning simply use a mild soap and water – other cleaners are not necessary. Copper will naturally patina over time and develop a warm medium patina. Unless you want to maintain a shiny copper finish, do not use copper cleaners. Do not use abrasive materials or harsh chemicals such as Comet. Rinse sink after each use, then dry with a soft cloth to remove any water spots.
Maintenance: To help a copper sink keep its patina for a longer period of time, use a carnauba based paste wax, applied monthly. ALWAYS dry your copper sink after each use.
If your copper sink has a dark spot from an item sitting in it too long, use a yellow & green sponge such a Scotch Brite and gently rub the dark area until it begins to lighten, then allow the natural patina to do its natural work. You may also try a paste of baking soda and water applied with a sponge.
Do not leave acidic foods such as tomatoes, tomato paste, lemons, or margarita mix sitting in your sink as they will leave a shiny spot in the sink. If this does happen, because copper is a metal that changes over time, the sink will recover its patina and blend in with the rest of the sink. The more use of the sink, the faster this will occur.
This finish will require the most maintenance and is the only finish that copper cleaners may be used to maintain the shiny appearance. Using a wax or a protective sealant will reduce the maintenance necessary to maintain the finish and delay the natural patina process.
Hand hammered polished nicked that darkens naturally over time, giving it a deeper finish. Care- After each use rinse with water and a soft cloth, DO NOT use anything abrasive such as Comet or Ajax as this will scratch the finish. Most common metal cleaners can be used to brighten the finish periodically.
Maintenance: Apply a carnauba based paste wax monthly to help the sink keep its shiny appearance. Buff with a soft cloth. As with an unfinished copper, you can use a wax or protective sealant to reduce the maintenance required.