2 Questions. Melting gold? Using acid on species?

Hey all,
Just a couple of questions. I have a few species and will be crushing them up over the summer into fines and hoping to melt them into a button so I can't lose them. Ive been looking around about the whole process and a lot of people seem to break crucibles regularly so I was looking at the cheap Chinese ones on eBay ($2.69 each) they are Quartz Silica crucibles and I was just thinking of buying say 4 of them and calling it sorted. Anyone tried these crucibles? Any good? for $2.69 a piece in not exactly expecting the best of the best, just do survive a few melts at least.

Secondly, I have a rather nice quartz specie where the veins all connect, I was wondering how to go about melting away the quartz and getting the spiderweb out of it. Never played with acid before and I know the stuff is dangerous so If anyone experienced could help me out with a bit of a walk through I would really appreciate it. Thanks all!

G'day AggrivatedSeaBass

Those crucibles should be ok, don't expect to much for that price, but you should get a few goes out of them. Heat up crucible and put about 1/4 teaspoon of borax in and let it melt all around the inside, then put in gold and get it bright red hot and add a little more borax and as the gold becomes fluid it should run together.

You can use an oxy torch for the heat source or a map gas torch, this takes much longer to get the gold to melt.

As for the acid treatment, it would be much better if your not experienced in doing any thing with acid is NOT to. You will need the very dangerous HF acid (hydrofluoric acid) there are no second chances with this stuff it is very dangerous.

If you just want to clean it up a bit then use Alibrite or Stainless Steel Pickling Paste, these have a low percent of HF in them.

cheers dave

Thanks for the reply davsgold.
The melting sounds simple enough then, so after I melt borax all over the crucible, add the gold, do I add borax before or after I start to heat the gold?
As for the acid Im using it to melt the quarts out of a specie so Ill have to use the acid. Ill try asking a couple of old prospectors around town, maybe theyll be more experienced in doing it and could help. Im scared of melting my arm off to be honest

AggrivatedSeaBass wrote: The melting sounds simple enough then, so after I melt borax all over the crucible, add the gold, do I add borax before or after I start to heat the gold?

After the initial borax to coat the new crucible add the gold and get it hot and then add a bit more borax, it acts like a flux and traps any bits of dirt grit quartz etc in the borax/flux, it ends up like a glass coating on the outside of the gold and just cracks off.

As for the acid get plenty of help/advise before attempting or using HF acid, it is NOT to be played around with, do a google search on HF acid and read it throughly.

cheers dave

davsgold wrote:

AggrivatedSeaBass wrote: The melting sounds simple enough then, so after I melt borax all over the crucible, add the gold, do I add borax before or after I start to heat the gold?

After the initial borax to coat the new crucible add the gold and get it hot and then add a bit more borax, it acts like a flux and traps any bits of dirt grit quartz etc in the borax/flux, it ends up like a glass coating on the outside of the gold and just cracks off.

As for the acid get plenty of help/advise before attempting or using HF acid, it is NOT to be played around with, do a google search on HF acid and read it throughly.

cheers dave  

with Dave is 100% correct there Aggrivatedseabass you do NOT want to mess with HF Acid here is a link have a good read.

http://en.m.wikipedia.org/wiki/HF_acid

Those quartz silicate crucibles are brilliant , I've been using the same one for about 5 years now.

Once you've melted it into a button, push it out immediately into some hydrochloric acid and the melted borax just drops off wi4hout having to dig and pick it off. This also stops that sunken melt mark from forming and leaves the surface smooth as a babies bum.

Drop the button back into the crucible the other side up, heat until molten and smooth and then drop back into the hydrochloric acid again.

You end up with a perfectly smooth and uniform button with no borax and no cooling dimples.

That's if you want to be a pedantic and anal button melter like me

HF acid took this from this


To this, 3oz after treatment that looks fairly neat

Thanks for the help guys! Plenty of good info there to get me going. Will make sure I put pics up of how it all goes. Yeah the HF acid has me shakin in my space boots. Deadly stuff. Will make sure I read that properly a few times before trying anything. That specie came up great, hope mine comes out that good

Gday Bass
There was an interesting post on here some time ago where one of the guys cut specie gold into cabochons and made rings out of them. Looked great. Just an idea.
I used HF acid extensively back in the 80's and was just dead lucky I reckon. Wouldn't touch it again.
cheers
Brett

Hey mulgadansa! Yeah that's an awesome idea. I'll definitely look into that. I'm not sure if the one I have is big enough though, any recommendations as to where to get it done?

Gday Bassy
Don't know where but here's how http://www.gemsociety.org/article/fundamentals-of-lapidary-part-4-cabochon-cutting/
I reckon a backyard hobby lapidiarist could do it. Maybe try a local gemstone club?
cheers
Brett