Stars on Gold bar

[Gold.refinery]

Hi

Stars on the surface on Gold bars after Refining!!!

After refining operation by AR method, our purity was 999.6 gold and 0.4 copper.
We added some silver for 995.
After the final melting, a number of stars were found on the surface of the gold bar.

What is this problem about?
what's the solution?

 

[orvi]

Maybe some wild crystal phase which evolved from the melt if it cooled slowly. Never seen this before.

 

[Lou]

How are you making the bars?

 

[Gold.refinery]

How are you making the bars?

You mean the type of furnace?

 

[Lou]

As in the process of making them.

 

[Gold.refinery]

May you ask in detail?

 

[4metals]

Do you cast bars by hand pouring and torch cooling?
Do you use an atmospheric tunnel bar machine?
Do you roll and stamp bars?
What process do you use to get your refined gold into sale-able form?

 

[Gold.refinery]

No,
Our furnace is a vacuum casting furnace.
Yes, if the ingot surface is good, we will stamp.

 

[Lightspeed]

i did see once an occasion where Ralph forwarded me a pic of a gold pour which revealed a simmilar pattern only more prominent, simmilar in detail and feature to the same phenomenon when pouring silver bars of decent purity which is why i had consulted Ralph on the topic. I could not get my head around the issue as it was 9995+ silver and should not have had impurities revealing this sort of thing.

The only thing that helped was to cool and let the metal soldify in the mold inside the furnace, very hot atmosphere instead of open air, but Ralph did state that the irridescent star pattern on silver was an indicator of purity.

As your gold has been dialed down to 995 i am really not sure but is maybe due to atmospheric condition. Its hard to say that the silver addition was the cause, i have never had the issue on my gold melts at 999.

Does the silver create a molecular crystal skin non homogenous to the gold as the solidification temperature and metal density is different is hard to say.
Stir with a carbon rod before pouring or swish the metal around in molten state before pouring?

 

[cejohnsonsr1]

This is out gassing. The gold probably isn’t quite as pure as you think and you probably didn’t get all the chemicals rinsed off before melting.

 

[silver1]

i did see once an occasion where Ralph forwarded me a pic of a gold pour which revealed a simmilar pattern only more prominent, simmilar in detail and feature to the same phenomenon when pouring silver bars of decent purity which is why i had consulted Ralph on the topic. I could not get my head around the issue as it was 9995+ silver and should not have had impurities revealing this sort of thing.

This is not the same effect here. What you are referring to is the holographic crystals formed on the surface of high purity materials. This is a contaminate issue we are seeing here.

 

[Lightspeed]

Yep that's it, Ralph sent me a stack of pics for my reference for comparison to my bars I was pouring

 

[silver1]

Yep that's it, Ralph sent me a stack of pics for my reference for comparison to my bars I was pouring

Palladium = Silver1 = Ralph

 

[Lightspeed]

Omg mate, I will pm you, so happy now.

 

[silver1]

Yes sir! Holler at me.

 

[Lino1406]

Some metals, e.g. aluminum form intermetallic compounds with gold, which appear as additional phases

 

[Gold.refinery]

last operation, we washed the gold powder with ammonia. We dried the powder in a steel container by heat. But finally you see the final level of the ingot below. Not good.
The white layer on the second photo was shown on the XRF , more Fe and less Cu.
Where does the problem come from?

 

[Gold.refinery]

The white layer on the second photo was shown on the XRF , more Fe and less Cu.

In the gold powder melting step, in last operations, I used the new crucible and did not add any additives during melting.

In the end, when the melting pool formed,
I looked at the melting pool, there was some white surface and the surface of pool was not shiny.

Are these the same impurities?

Am I allowed to use some Borax to remove the impurities?

 

[Yggdrasil]

last operation, we washed the gold powder with ammonia. We dried the powder in a steel container by heat. But finally you see the final level of the ingot below. Not good.
The white layer on the second photo was shown on the XRF , more Fe and less Cu.
Where does the problem come from?

I wold guess the steel container.
Minute particles of iron along with weak acid residue in the gold powder maybe.

How did you get it out of the steel container? Some kind of brush, scrape or pure gravity?

 

[Gold.refinery]

Some kind of brush, scrape or pure gravity?

With a wooden spoon