Just like silver, bronze will eventually oxidize, although most of our bronze jewelery contains a ceramic layer to prevent/slow down oxidation. Bronze that oxidizes darkens in color, which gives the metal a nice, somewhat antique touch. Normally, the darkening happens evenly, but cosmetics or chemicals
can cause other (or even green) effects. Water and (hand) soap are no problem.
When your bronze gets darker, 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 appearance, this is harmless and can wash you off. If you want to avoid this, it is advisable to keep the ring as dry as possible and possibly go over the inside of the ring with the abrasive side of a scouring pad.
Nina Designs is a jewelry brand with a heart of gold that makes fair trade jewelry in Thailand and Bali and tries to work as ethically and ecologically as possible. Their wages are well above the national minimum wages, employees receive a thirteenth month, 3 months of paid maternity leave, education about pre- and post-natal care, pension savings, etc. In their studio in Bali, 50% of the managers are women, which is even more impressive there than here.
Nina Designs uses recycled silver as much as possible. For each parcel sent, a tree is planted, which is part of a so-called "forest garden". The jeweler gives micro loans to starting craftswomen and supports various NGOs that fight for human rights, literacy or the environment. And of course their silversmiths also make beautiful jewellery!