I vaguely remember being told, when I purchased some copper clay a while ago, to put the piece inside a fibre blanket, ie, fibre top and bottom..........but as I haven't tried it, I cannot really advise further.  I recommend you try asking the seller/manufacturer of the product.

Hello,

Has anyone out there tried using their enamel kiln to fire Copper metal clay (or
any other base-metal clay)? I've read online that the clay needs to be fired in
activated coconut carbon to prevent oxidation.

Does the carbon stain the inside of the kiln when the metal clay is fired? Today
I saw a kiln that was used to fire metal clay, and the inside of the firing
chamber was absolutely coated in black soot or metal oxides. This is not
something that I would want happening to an enamel kiln. The kiln owner said
that she thought the kiln coating was due to firing the clay and carbon in a
steel pan, rather than firing the clay or the carbon themselves.

Would the black coating of the kiln be prevented if the metal clay was fired in
a ceramic vessel that contained the activated coconut carbon, or would the
carbon itself contribute to the contamination of the kiln?

I would be very interested in experimenting with base metal clays like copper or
brass, provided that using these materials wouldn't interfere with my
enamelling.

Thanks for any advice!

Christine