Melting gold - crucibles - advice sought

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Melting gold - crucibles - advice sought

Post  AnnieL on Thu Aug 16, 2018 5:43 pm

G’day everyone.
I recently sought help from a friend of mine to melt down some of my gold. He had a very simple method, using a crucible secured in a vice, Hot Devil gas bottle from Bunnings and made them into 1 oz slugs. (I have done a forum search and seen some things posted by Davesgold about a Hebel block and Johnnie but I want to keep it simple, not really into furnaces).

I’m keen to just melt the gold nuggets into slugs or ingots of 1 oz or 2 oz.

So, I looks up crucibles on internet and it seems there are graphite ones and silicone ones. Would you give me your opinion on the best type to use and anything else you think useful. Pics would be a great help too. Very Happy

I’ve put in a photos of what my friend used so you ‘get the picture’.



Finished product - 5.5 oz, after a dunk in some acid he had.
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Re: Melting gold - crucibles - advice sought

Post  koeh on Thu Aug 16, 2018 6:25 pm

Put some borax in with the gold will make it melt a bit quicker, available from most supermarkets
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Re: Melting gold - crucibles - advice sought

Post  geof_junk on Thu Aug 16, 2018 8:15 pm

I used a fire brick and ground a bowl shaped hole in it. The smaller the gold melt the easier it is to melt. I used the cheap can gas.Propane or Butane has flame temperature of about 1960 to 1970 °C and Gold melts @ about 1064°C so they are acceptable for the job.

https://i.servimg.com/u/f72/19/88/70/23/melt-410.jpg

The five bits above the watch add up to 16+ ounces, 6 Oz is the largest.

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melting gold

Post  xmas tree on Thu Aug 16, 2018 10:03 pm

What happens to the quartz when you melt a specimen? Doesn't it have a higher melting point than gold?

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Re: Melting gold - crucibles - advice sought

Post  geof_junk on Thu Aug 16, 2018 10:39 pm

The gold go together when melted (just like bit of mercury does at room temperature ) and leaves the quartz behind like glass.
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Re: Melting gold - crucibles - advice sought

Post  Jen on Thu Aug 16, 2018 11:39 pm

we have one of these, does a great job, comes as a almost complete kit
We brought the burners from bunnings.

https://www.finderskeepersgold.com/product/kwik-kiln-kit-4/

Turns scrappy gold into this.  Very Happy


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Re: Melting gold - crucibles - advice sought

Post  HOBO'S Gold on Sun Aug 19, 2018 9:57 am

AnnieL wrote:G’day everyone.
I recently sought help from a friend of mine to melt down some of my gold. He had a very simple method, using a crucible secured in a vice, Hot Devil gas bottle from Bunnings and made them into 1 oz slugs. (I have done a forum search and seen some things posted by Davesgold about a Hebel block and Johnnie but I want to keep it simple, not really into furnaces).

I’m keen to just melt the gold nuggets into slugs or ingots of 1 oz or 2 oz.

So, I looks up crucibles on internet and it seems there are graphite ones and silicone ones. Would you give me your opinion on the best type to use and anything else you think useful. Pics would be a great help too. Very Happy

I’ve put in a photos of what my friend used so you ‘get the picture’.



Finished product - 5.5 oz, after a dunk in some acid he had.
Sorry just saw this post, Melting 1oz to 2 oz gold in the method you are doing will not work very well, due heat lose, I've tried in the early days with a silicone crucible with 2 mapp gas torches and it took soooo long and still didn't get the gold flowing, that's why I use the method I use with the furnaces I make. You can try the David method but hebal can't take the temperatures that my furnace can take, but it's a budget way of doing it.  With the dish Crucibles I find around 5grams and under is ideal because you can keep the flame concentrated on all the gold, as soon as the flame is off the gold it cools quickly. Hope this helps and good luck.
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Re: Melting gold - crucibles - advice sought

Post  davsgold on Sun Aug 19, 2018 4:08 pm

G'day Annie

I find that a single gas torch like in your picture takes forever to get the gold hot enough.

A simple furnace, like the Hebal block ones that I made are very effective at concentrating the heat around the Graphite crucible.

The Hebal block (600x200x200) cost $13 at Bunnings and I can cut 4 furnaces from 1 block using a wood hand saw and a hole saw to cut the main center hole,  and a drill and a 1/2 bit for the torch holes.  And the Hebal can take the same temps that the furnace Hobo makes, they may not last as long but they cost way less, the heat eats them away gradually just the same as it does with the graphite crucibles.

Make sure you get the bigger torch ends NOT the pencil torch ends they won't get the job hot enough, I know this and have seen this, the bigger torch ends will have the gold liquid in the crucible in about 5 minutes ready to pour.





cheers dave
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Re: Melting gold - crucibles - advice sought

Post  HOBO'S Gold on Sun Aug 19, 2018 7:39 pm

I don't use Hebel Dave so that's not correct. the materials I use take higher temperatures than Hebel.
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Re: Melting gold - crucibles - advice sought

Post  davsgold on Sun Aug 19, 2018 9:37 pm

HOBO'S Gold wrote:I don't use Hebel Dave so that's not correct. the materials I use take higher temperatures than Hebel.

Yeah I know you don't use Hebal, you brought up Hebal and I was just sayin.  Gold melts at 1065 deg Celsius, and Hebal can take temps up to 1200 to 1500 deg Celsius, which is way above golds melting temp, and I realize the material you use can take temps up to 3000 deg Celsius, my furnace costs are way way less than yours, just sayin, yours are great and well made and you sell them, I just make mine for my own use and anyone that wants to make their own I will let them know how and what to use.

I am not trying to start an argument about yours is better than mine or vise/versa, Annie was asking about what different options people use and that is what I use. Very Happy  all good mate. Very Happy

cheers dave

PS: I did say, "And the Hebal can take the same temps that the furnace Hobo makes" which when your using either furnace neither are getting above 1200 dec C and more like 1180 deg C so no harm is happening to either type of furnace. Very Happy
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Re: Melting gold - crucibles - advice sought

Post  AnnieL on Mon Aug 20, 2018 7:42 pm

Thanks for the feedback guys and Jen.

I was there when my friend melted the gold as shown in my pic and it seriously didn’t take that long. Just weighed up in 1 oz lots and melted it. Maybe I just need to find heaps more gold and do larger melts  Laughing

I still have one question - is there anything significant in the difference with graphite or silicone crucibles ie: is one thought to be better than the other?

Thanks in advance.

Cheers
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Re: Melting gold - crucibles - advice sought

Post  Guest on Mon Aug 20, 2018 8:03 pm

Hebel is porous, so you can lose gold into those tiny little holes. Shocked

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Re: Melting gold - crucibles - advice sought

Post  Jen on Mon Aug 20, 2018 8:20 pm

Annie
All I can find out about the difference between the crucibles is that the silicon ones are more for small amounts of melting gold

http://www.alloyavenue.com/vb/showthread.php?11246-Difference-between-Graphite-and-Fused-silicon-Crucibles

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Re: Melting gold - crucibles - advice sought

Post  davsgold on Mon Aug 20, 2018 8:42 pm

UNCLE BOB wrote:Hebel is porous, so you can lose gold into those tiny little holes. Shocked

Mate the gold sits in a crucible inside the furnace, and besides that when the furnace is stuffed I crush the inside and pan it off Very Happy Very Happy Very Happy

cheers dave
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Re: Melting gold - crucibles - advice sought

Post  Guest on Mon Aug 20, 2018 10:15 pm

davsgold wrote:
UNCLE BOB wrote:Hebel is porous, so you can lose gold into those tiny little holes. Shocked

Mate the gold sits in a crucible inside the furnace, and besides that when the furnace is stuffed I crush the inside and pan it off Very Happy Very Happy Very Happy

cheers dave

cheers

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Re: Melting gold - crucibles - advice sought

Post  joe82 on Tue Aug 21, 2018 6:17 am

whats the best little torch to heat with don't want to have to buy big oxy setup??? just getting into this melting thing and need to get setup cheers joe,

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Re: Melting gold - crucibles - advice sought

Post  davsgold on Tue Aug 21, 2018 9:56 am

joe82 wrote:whats the best little torch to heat with don't want to have to buy big oxy setup??? just getting into this melting thing and need to get setup cheers joe,

G'day Joe

I use two of these from Bunnings and they fit on top of either the yellow map gas type bottles or the green buddy type bottles.

https://www.bunnings.com.au/tradeflame-tf-ultra-gas-performance-gas-stainless-steel-blowtorch-with-piezo_p5910236

https://www.bunnings.com.au/tradeflame-tf-ultra-gas-performance-gas-mapp-replacement-3-pack_p5910239

cheers dave
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Re: Melting gold - crucibles - advice sought

Post  HOBO'S Gold on Tue Aug 21, 2018 9:27 pm

joe82 wrote:whats the best little torch to heat with don't want to have to buy big oxy setup??? just getting into this melting thing and need to get setup cheers joe,
These are the one's I use, they are so much better than the Bunnings one as a few I know had the Bunnings one's fail. TS4000 or TS 8000 are better. https://www.ebay.com.au/itm/Hampdon-TS8000-Style-Blow-Torch-Kit-for-Brazing-Soldering-Mapp-Gas-Map/122365192717?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649
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Re: Melting gold - crucibles - advice sought

Post  joe82 on Sat Aug 25, 2018 6:37 am

sweet guys cheers for the heads up I will grab one next time im in Townsville cheers

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