9K yellow gold having pink hues after polishing.

[soberleuter]

Hi, I seem to have some problems after I melt scrap gold in my electric furnace, I then add some boric acid, pour into a delft clay casting ring, and clean it off. But here is where I find a have trouble. When I have soldered and assembled my pendant, I then start to polish with rotary tool, using different types of abrasives, and my metal starts to get a pink hue. I will then reheat it, add it to t her pickle a number of times until all the pink seems to have vanished. But still hints of it. It’s making me go crazy… hahah… please need any help you have!

Photos aren’t great sorry… but the gold seems to pour nicely into the mould… but as soon as I start to abrade any extra metal or polish with my emery paper, or 3M polishing wheels it will turn pink. Underneath the blue Opal it’s very pink!

 

[soberleuter]

View attachment IMG_9860.MOV

 

[Yggdrasil]

Hi, I seem to have some problems after I melt scrap gold in my electric furnace, I then add some boric acid, pour into a delft clay casting ring, and clean it off. But here is where I find a have trouble. When I have soldered and assembled my pendant, I then start to polish with rotary tool, using different types of abrasives, and my metal starts to get a pink hue. I will then reheat it, add it to t her pickle a number of times until all the pink seems to have vanished. But still hints of it. It’s making me go crazy… hahah… please need any help you have!

Photos aren’t great sorry… but the gold seems to pour nicely into the mould… but as soon as I start to abrade any extra metal or polish with my emery paper, or 3M polishing wheels it will turn pink. Underneath the blue Opal it’s very pink!

The best forum for this kind of question may be Ganoksin Orchid which is a forum for jewellers.

 

[Yggdrasil]

Hi, I seem to have some problems after I melt scrap gold in my electric furnace, I then add some boric acid, pour into a delft clay casting ring, and clean it off. But here is where I find a have trouble. When I have soldered and assembled my pendant, I then start to polish with rotary tool, using different types of abrasives, and my metal starts to get a pink hue. I will then reheat it, add it to t her pickle a number of times until all the pink seems to have vanished. But still hints of it. It’s making me go crazy… hahah… please need any help you have!

Photos aren’t great sorry… but the gold seems to pour nicely into the mould… but as soon as I start to abrade any extra metal or polish with my emery paper, or 3M polishing wheels it will turn pink. Underneath the blue Opal it’s very pink!

Your issue may be related to that you melt scrap.
When melting scrap you have little control over what is in your metal, and even more so with low carat scrap.
Even if you have control of where the scrap comes from, remelting scrap will change its properties due to the volatility if some elements in the alloy, like Zinc and others.
The best way out is to fully refine the Gold and then creating a fresh alloy.

 

[FrugalRefiner]

Your issue may be related to that you melt scrap.
When melting scrap you have little control over what is in your metal, and even more so with low carat scrap.
Even if you have control of where the scrap comes from, remelting scrap will change its properties due to the volatility if some elements in the alloy, like Zinc and others.
The best way out is to fully refine the Gold and then creating a fresh alloy.

Adding to that, every time an alloy is melted, some of the base metals, like copper, oxidize during the melt, so you end up with problems in your castings, like porosity.

It is best to refine your scrap, then create fresh alloys for your castings.

Dave

 

[stella polaris]

Let me guess the 9k is gold/copper. It will give a "red" (pink) gold. If Gold/silver it should not

 

[nickvc]

All large manufacturers cyanide strip their products which removes the copper layer and leaves the clean gold below , the problem with 9 carat is that it’s a copper alloy by percentage , you could try heating your items and covering with borax once red hot that should stop the copper oxidizing , you will have to clean the item and weak sulphuric should do that , it may be easier for you than sourcing cyanide .

 

[Martijn]

Different mixes of gold/silver/copper in a color chart:

 

[stella polaris]

All large manufacturers cyanide strip their products which removes the copper layer and leaves the clean gold below , the problem with 9 carat is that it’s a copper alloy by percentage , you could try heating your items and covering with borax once red hot that should stop the copper oxidizing , you will have to clean the item and weak sulphuric should do that , it may be easier for you than sourcing cyanide .

Do you mean they remove surface copper in order to get a more "gold look". Could not a dip in nitric give the same results or is it too much gold in 9 k?

 

[nickvc]

Nitric is worth a try but do it after heating your item and use clean acid.

 

[soberleuter]

Thanks so much for all the help! I try and recycle and reuse gold, but will do more refining before casting. It never happened when I would just buy the gold granules, but ever since I started buying recycled gold it seems to have this issue. Amazing! Thanks again!!