Each manufacturer is using different methods for creating antique copper. Some suppliers use more environment friendly ways of ageing copper and others employ chemicals. How it works? Copper is getting dark in natural process and changes from shining light tones into dark coffee. It takes a long time for metal to become antique looking. In Mexico most producers use heat to accelerate darkining and then use a special paste to prevent further edging. So our copper vent hoods, tubs, sinks and tables have permanent finish.