bringing up the gold

[ajda]

I'm rolling a small piece of 18ct red gold sheet. Presumably repeated annealing and pickling has the effect of depleting the copper, leaving a higher concentration of gold (and silver) on the surface, just like "bringing up" fine silver to the surface of sterling. If that's the case, I'm assuming, ultimately, that I can polish it back to the original red colour. How deep is the copper-depleted layer likely to be?

Alan

[enigma]

What are you rolling from and to?
I generally find I can roll mine without annealing and only anneal at the end but obviously it depends how much you are rolling down.

[ajda]

I'm not actually rolling very much - from 0.5 to about 0.4mm, perhaps a bit thinner - but will be forming in other ways and doing some soldering - so I'm assuming repeated pickling will be needed.
Alan

[Goldsmith]

Yes Alan, the polishing will return the red gold colour, the depth of depletion colour is minimal, and there is no need to pickle after each annealing on 18ct .

James

[ajda]

Thanks for that, James. Do you judge the need for pickling on the basis of how black it looks after torching? And out of interest what do you think is best for 18ct? I'm using sulphuric acid (approx 10%).
Alan

[Dennis]

Someone might comment on the holes in your clothes, or even drop a £ in your hat Alan.

[Goldsmith]

Thanks for that, James. Do you judge the need for pickling on the basis of how black it looks after torching? And out of interest what do you think is best for 18ct? I'm using sulphuric acid (approx 10%).
Alan

I use 20% dilute sulphuric acid pickle for everything and have done for 50+ years. Fire stain is very little on 18ct golds, when making small items I usually only pickle after soldering, I like to file solder joints to remove surface metal and leaving the best clean surface, pre fluxing and soldering. For multiple soldering I will pickle after each soldering element but I still like to file the next solder joint surface. I also use a scraper to clean the solder surface before cutting solder pallions pre fluxing.


James

[ajda]

Thanks again, James - that's a great help.

And thanks, Dennis, but I don't need the £ as I'm launching my high-end fashion range:

[ajda]

Another couple of minor questions...
1. When annealing or doing any other torch work with 18ct, should you always flux all over?
2. Do you quench in water only? I've read about people using pickle or dilute alcohol in some cases.
Alan

[Goldsmith]

I can only say what I do, I don't know what the books or college tutors say is the correct way.
1. When annealing gold or sterling silver I do not cover with flux or anything and never have.
2. I never quench gold or silver in water after annealing, I usually just place the annealed metal onto my steel block after it has cooled down for a few minutes on the fire brick I anneal on.

Also I never place hot items in the pickle.

James