Alongside the traditional copper casting project I have done a copper/silver cast; using plumber’s copper and silver.
and two-part sand moulds. This is partly sustainable, with all materials being recycled; but the heat used is gas.
One of the pieces sold unfinished at ENOS 2018. The bowl has a metal ‘pebble’ inset, a blue heat patina and is almost clean copper on the exterior because I used a different greensand on the outside.
Some learning – try different sands to give cleaner surfaces but retain textures, cost in the silver, keep experimenting, copper is an attractive metal although challenging to work with.