Interloper!

Hi from Kent. I'm not a jeweller but a sculptor/installation artist. Have discovered enamelling and am planning a project. Just bought a mini-kiln and my first batch of copper 'leaves' (bought from Cookson's) have turned out very inconsistently. I know that happens but I want the right inconsistency!

Main issue: they are coming out black on first firing, even before using any flux. If I use flux they turn completely black and it doesn't flake off.

I'm firing at 820 for about 2-3 minutes. Some of the blackness pops off as they cool but I don't want any black.

Any advice from more experienced enamellers (on copper)?