Like silver, bronze will eventually oxidize, although most of our bronze jewelry contains a ceramic coating to prevent/delay oxidation. Bronze that oxidizes becomes darker in color which gives the metal a nice, somewhat antique touch. Normally the darkening happens evenly, but cosmetics or chemicals
can cause different (or even green) effects. Water and (hand) soap are not a problem.
When your bronze darkens, you can rub it clean with a flannel cloth, possibly with a damp cloth with a little ecological detergent. Then dry your jewel well.
For some people a bronze ring can leave a green-black shine, this is not harmful and can be washed away. If you want to avoid this, it is advisable to keep the ring as dry as possible and possibly occasionally go over the inside of the ring with the abrasive side of a scouring pad.
Nina Designs is a jewellery brand with a heart of gold. They make fair trade jewellery in Thailand and Bali and try to work as ethically and ecologically as possible. Their wages are well above national minimum wages, employees receive an extra month's wage as an end-of-year bonus. In addition, workers receive a food allowance for lunches. The company provides health care, with a doctor on call for staff medical needs. Expectant mothers receive education about prenatal care and safe delivery. Mothers receive three months paid maternity leave or six months on half pay. Their hospital fees are also covered. In Bali, fifty percent of managers at the production facility are women, a figure that is even more impressive in Indonesia than it would be in the EU.
Nina Designs uses as much recycled silver as possible, and for every package they send, they plant a tree that will be part of a so called "forest garden". They give out microloans to skilled women artisans and support different NGO's for human rights, literacy and the environment.