Non-Chemical Gold gone bad !!

[blakeyvision]

Hi everyone

Im a alittle confussed :roll: about something im alittle wet behind the ears and new to home refining.
But I got myself a mini furnace really mini does max about 4 oz of gold really didnt want to punch above my weight and get nothing big at the moment.
Anyway I got it up to heat just for a trial and placed a tested and marked 14k russian gold hoop earings which were 2.4 grams It melted straight away telling me it was up to temp. When I took it out that nice gold colour was now not gold but black in colour what have I done wrong ?
What I did do was I did not pour but just let it cool in the crusible after switching the furnace off is this my own doing ? or have I been given lead

Any info would be cool

 

[butcher]

14K is about 58% gold, as 42% other metals, if it was karat gold you melted you most likely just oxidized the other metals in the gold.

 

[blakeyvision]

Sorry for being a simpleton but when I see other people melt 14k gold it comes out gold in colour how would I remove the other metals? :roll: Acid?

 

[butcher]

Well first thing would be to read Hokes book.

This will help you understand this question and many others about gold, and recovery and refining the metals, and much about these metals in jewelry.

Jewelers normally will not re-melt to make karat gold to make jewelry, they make the karat gold from pure metals, because of what you experienced.

Although you can help to prevent somewhat the oxidation of base metals with the type of atmosphere the base metals are melted in, with things like a reducing atmosphere, reducing flames or reducing flux, but even these techniques are not good for making jewelry, which normally will need to be soft enough to be worked.

Also jewelry may contain things like solder, or other metals in clasps or parts, that if melted with the jewelry, would not only lower karat of the melt, but can also add other metal contaminants to the melted metal alloying in with it, ruining the ability to work the metal at all.

I am not a jeweler so I am not qualified on this subject.

Read Hoke's book, you have no Idea of what you are missing until you do read it.

 

[g_axelsson]

I've made some gold castings with 18k gold and they always comes out from the casting as a black to brown metal. Jewellers are using a pickling bath (sulphuric acid or some other stuff, it varies) to remove the oxidation of the surface.

The only way you could have carate gold coming out of a melt without any oxidation is to melt it in a reducing atmosphere or under vacuum, keeping oxygen from the melt.

Göran

 

[blakeyvision]

I will try and locate some acid and give it a go just was shocked to see a black button instead of gold the missis went nuts when she saw what I had made her earings into :lol: thanks chaps

 

[blakeyvision]

I just tried putting it in cola and left in for 3 hours it has came up nice and golden god bless coca cola :lol:

 

[g_axelsson]

:lol: That feels soo good, I just ate burger meal with a big glass of cola.

An ancient recipy from nortern Scandinavia is fermented lingonberrys, they are so acidic that it works just as good as cola, silver smiths here used it before sulphuric acid got common.

Göran