Hi all, I’m looking for any advice or knowledge on gold casting. I’ve been trying to make a cast ring (with the rough finish left). I’m using delft clay and the mould part has been going ok. However the first couple of attempts weren’t quite right so I remelted and tried again. On the third attempt, when I removed the gold from the mould it has turned a coppery colour and lost its gold colour. I’ve tried polishing and even filling back but it seems to be all the way though rather than just a coating.

Have I ruined my gold (9k) or is it reversible? Also if it is ruined how would I prevent this in the future? I have searched everywhere for information and from my research I believe the gold has oxidised?

Thanks for any help possible!