Copper is not the new black!

[Nemesis]

I am sculptor/installation artist starting a project making multiple pieces of fired copper. I 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!

The main issue is that 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. I can manage to 'polish' off some of the black but as I am making many of these it is unfeasible to do this with every one.

[CJ57]

It would be helpful to see a pic of what you are making and the problem. It's my understanding that you are making the leaves from copper clay? Not knowing what size they are, have you thought about forming them from sheet which is much more dependable?

[Dennis]

You are not the only one with this complaint: https://www.google.co.uk/search?q=copper+clay+pieces+black&ie=utf-8&oe=utf-8&client=firefox-b&gfe_rd=cr&ei=f2NuWMC8A4aCaLn6peAK

Happy reading, but Nancy Hamilton says it will come off in pickle. As fired clay is porous, any residual pickle should be neutralised in a solution of hot soda crystals.Dennis.

[Nemesis]

Hi Caroline,
Thanks so much for your reply. Here are some photos which I hope will illustrate the problem:

The first is the copper templates unfired, bought from Cooksons9762

The second is after firing at 800 for 2-3 minutes9763

And the third is after applying one coat of clear flux9764

As I'm sure you know these little templates aren't cheap and I feel I'm wasting them....any ideas?

[metalsmith]

Hi Caroline,
Thanks so much for your reply. Here are some photos which I hope will illustrate the problem:

The first is the copper templates unfired, bought from Cooksons9762

The second is after firing at 800 for 2-3 minutes9763

And the third is after applying one coat of clear flux9764

As I'm sure you know these little templates aren't cheap and I feel I'm wasting them....any ideas?

Have you tried the enamelling on just plain copper sheet? It would be useful to know if the clay is the root of the problem or the copper. Since copper enamelling blanks are sold, I wouldn't have thought the problem would be there. Sorry I don't know much about enamelling copper, but just first principles say to cut the complexity and reduce the degrees of freedom.

[ps_bond]

I assume that these are 860-227 (which are not clay).

Daft question - why are you firing the copper blanks without enamel on them? All you'll do is create an oxide layer.
Normal enamelling practice would be to clean them, coat them with enamel then fire. Not that I do much.

The oxides on the uncoated, fired pieces will clean off in pickle.

[Goldsmith]

It would be useful to know what you are trying to achieve, most of us metalsmiths would do any metal colouring after the job is constructed, not before construction. It may be worthwhile you joining this FaceBook Group for copper colouring advice;https://www.facebook.com/groups/333399403381755/

James

[Nemesis]

Sorry, I don't know what you mean about clay...? These blanks were just fired...direct into the kiln, no additional anything.

[Nemesis]

Thanks for your reply. It is a sculpture/installation and the copper leaves will be attached to it....?

[Nemesis]

Thanks for this. Yes, these are copper, not clay.

In a class I attended we were told that firing 'cleaned' the copper before putting anything on ...?

Daft question - what's pickle?

[Nemesis]

Thanks James...I'm not a metalsmith...I think the FB group is more for jewellers.

[ps_bond]

Thanks for this. Yes, these are copper, not clay.

In a class I attended we were told that firing 'cleaned' the copper before putting anything on ...?

Hmm. Can't quite fathom why that would be said without context, but I'd clean the metal with pumice, Scotch stone (if you can find any), wet & dry or similar abrasive. If you want *really* clean, there's the water break test, but that's possibly overkill. Unless the pieces are fired and then pickled, that would burn any grease off but would leave a matte surface after pickling.


Daft question - what's pickle?

Acid, dissolving oxides for the use of. 10% sulphuric is good, but the use of e.g. sodium bisulphate (safety pickle) is a safer solution. Warmed, it'll reduce copper oxides to copper sulphate (turning the pickle blue, of course).
There's several other solutions (no pun intended) including citric acid, salt & vinegar, alum and so on.

[Goldsmith]

Perhaps if you could say what you intend doing with the copper leaves we could give advice. Are you going to shape the flat leaves? are you going to make the leaves into sprays of leaves? are you going to texture the leaves? are you going to colour or enamel the leaves?
Sorry if I am asking a lot of questions, but most of my past work has included life size leaves and flowers as decorations, although I only use copper for making patterns.

James

[CJ57]

Sorry, I thought because you were putting them in the kiln that they were made from copper clay otherwise not sure why sheet would need fired. As everyone else has said they either need cleaned with pickle to take the oxides off or with wet and dry to clean by hand. I see they are sold for enamelling or reshaping so would imagine they are ready to go.