Silver 925, also known as Sterling Silver, contains 92.5% silver and 7.5% copper. Pure silver is not used in jewelry making, as it is too soft. Silver has a seductive look with its warm color-temperature and has been used in jewelry making since ancient times. The disadvantage of silver is: It can react to sulfur in the air (depending on air quality and skin type). This is commonly known as ´tarnishing´ or ´oxidation´. The best way to remove these dark spots is the following: polishing cloth boil water in a pan and add some salt and a piece of uncoated aluminium foil. Then put your piece of jewel into the pan and "pickle" it wait for a while. Effective are also polish products especially made for silver-cleaning.