You will need
  • Crucifix, water, liquid dishwashing, ammonia, tooth powder, soda.
Blacken, as a rule, copper, brass and bronze crosses, and silverware (especially the alloy with copper) or gold low sample. This happens because of a chemical reaction of sweat, sebum as well as moisture and oxygen contained in the air, with the metal of that cross.
People who are inclined to a mystical view of things, suspicion and fears, I can say that darkening a crucifix – a sure sign of impending disaster. For example, it is believed that the owner of the darkened cross will certainly get in a bad life situation, get ill or die. Oddly enough, their fears are not without certain grounds. For violations of exchange of substances in the sebum may increase the sulphur content. Sulfur reacts with silver and copper comprising the alloy from which cast the Church's crosses, and decoration darkens considerably. However, not only the body of the sick person secretes increased amounts of sulfur. This occurs, for example, when hormonal changes caused by pregnancy. A lot of sulfur contained in the organisms of people who prefer to eat legumes, eggs and fish.
A perfectly healthy man, whose body is not saturated in sulfur, too, can discover his cross went dark. It's enough to live in areas with a humid climate, especially on the coast. But if near the home of the owner of the Church decorations is a chemical manufacturing and often smell of hydrogen sulfide, then cross byblack almost certainly. However, this is the case, when the people's superstition is absolutely true: if you do not move away from the dangerous neighbourhood with an industrial facility, it may face trouble with health.
Least likely to blacken crosses, made in good jewelry shop of gold of high purity. The reason is simple. Jewelers value their reputation and don't try to cheapen their products by adding to the alloys of copper, Nickel and other "base" metals. Church of the master trying to make an inexpensive mass crosses, so often quality suffers.
Seeing that the cross darkened, do not panic. This is not mysticism and not the punishment of the Lord, and ordinary chemistry. You can clean the cross or to replace it with a more expensive one.