9k gold casting - ruined?

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!

Hi and welcome to the forum.
If the red colour is really all the way through, this is probably caused by burning off the zinc in the alloy, due to repeated melting, allowing the copper colour to supervene. Don't despair, red gold is actually very popular and can look quite smart.

If it turns out that the red colour can be polished off after all, then it can be caused by dipping steel implements in your pickle, or contaminating it with stray iron bits. It can be restored by putting the ring back in fresh warm pickle and adding a dash of hydrogen peroxide, if you can find some. Dennis.