Melting 'practice'

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Dr_Code

Dr_Code

Active member
Joined
Sep 21, 2012
Messages
26
I thought I was good with a torch. Nope. I turned 2g Au into .3g Au - the remaining 1.7g is somewhere on my grage floor.

I've read a lot of tips on how to melt. Keep the flame high, wrap in tissue soaked with alcohol, etc. Any ideas on a less expensive metal to practice on? I thought about filing off a bunch of steel, but I would think that would be too large of a 'grain'. Maybe a grinding wheel, and collect what comes off? Melt Borax? But that stuff fluffs up and blows all over the place no matter what I do when I prep a melting dish.[youtube][/youtube]
 
I used a map/oxy torchI thought I did enough circles above the dish things seemed to be getting melted near the edge. I moved in closer, and it mostly blew away. I did not preheat my melting dish, maybe that was my fatal flaw.
 
Grinding dust is burnt material, highly oxidized and just more problems.

Heat the borax treated dish to red, add the powder. Now adjust your torch to the smallest stable flame. The flame should be silent with no hissing and start working the edges. Once it's all golden on top you can bump up the flame again.

Even when you work carefully if you do this on a piece of fire brick in the middle of a cookie sheet you can save all the microscopic gold balls that try to get away. If nothing else work on a clean surface you can sweep up after.
 
Thanks for the replies.

I'm not looking for something to add to the Au. I'm looking for something similar in properties to the Au dust that I can practice melting on.
 
ok now ive never used a melting dish before or melted any metal before for that matter but i have seen people blow there metal out of the dish with to much flame. so i thought about this problem alot. what ive come up with is this if you take your metal dust be it Au or silver or any kind and place it in a Cooking Ramiken and add water the let the water evaporate the dust will stay in a clump form so it wont be loose dust and it wont fly out of a melting dish. though as i said earlier ive never tried to melt metal before but i do have several 5 gram clumps ive made from Au and they feel tight so i dont think it will fly away on me the first time i melt them
 
Drowningbodacius said:
ok now ive never used a melting dish before or melted any metal before for that matter but i have seen people blow there metal out of the dish with to much flame. so i thought about this problem alot. what ive come up with is this if you take your metal dust be it Au or silver or any kind and place it in a Cooking Ramiken and add water the let the water evaporate the dust will stay in a clump form so it wont be loose dust and it wont fly out of a melting dish. though as i said earlier ive never tried to melt metal before but i do have several 5 gram clumps ive made from Au and they feel tight so i dont think it will fly away on me the first time i melt them
Click to expand...

place the powder in a small piece of tissue and roll into a ball. soak the ball in alcohol and let it dry.place the tissue ball in the melt dish and go from there.
 
Ah, that's the key!!!

I've read plenty of times to 'place it in tissue and soak with alcohol'. I guess I've always missed the 'and let it dry' part. I didn't think about it making a 'cake' like Drowningbodacius was talking about.

Plus, with the tissue paper, I can save the ramekins for the creme brulee. :)
 
How about using silver powder as a cheap test metal? It is easily dissolved in nitric and cemented as a fine powder on copper. The easiest way is to have too little acid to dissolve all silver, then it is just to cement when the acid stops working.

/Göran
 
Could try aluminum dust. Its light so it would probably have similar " blowing away" properties as gold powder, even if it's grain size was a bit larger. It melts at a bit lower temp than gold, but might be worth a try if your only after the " blow away" prevention. Just like others have stated. Never melt anything in your gold melting dish except pure gold! Doing so will contaminate your dish and any gold melted in it afterwards.

I believe that Geo's suggestion is probably the best one though while your still new at this.

I personally use a mapp gas torch to melt my gold. I believe that its called a turbo torch, or something silly like that. It does not blow very hard at all and just the other day I melted over 2 troy ounces of gold with it all at once. It took about 15 min to become a free flowing ball but the gold weight before and after the melt only differed by 0.2g. Not too bad, right? ( I used a dish bought from lasersteve's web store and a soft type fire brick with a bowl shaped area carved out of it that the dish sets in. ) This was all done outside in 40 degree weather too. I know many people don't like using mapp gas because they feel like they can't melt larger amounts of gold with it or it takes too long. But with the correct torch head and melting dish setup, mapp has served me well. I have not been doing this hobby long and I'm proud to say that I have been fortunate enough not to have any major vale losses. Its all due to everyone here on the forum sharing their knowledge and experiences. Thank you all!



Edited for spelling.
 
Straight MAPP gas (small yellow cylinder from Lowes) will melt up to 2 OzT of pure gold with no problem. The dish should be clean, dry, glazed with borax, and mounted in a hollowed out firebrick and/or insulated on the bottom with koawool. Start with the flame 12-16" from the surface of the plain gold powder in the prepared dish. Heat gently moving slightly closer as needed until the gold powder contracts to a sponge and begins to pull away from the upper edges of the dish (still brown, slightly golden hue). Once the gold fully dries and contracts into a more solid sponge, bring your torch close and begin circling the top of the sponge moving around as the brown sponge changes to liquid gold as you go.

The gold will not contract and sponge up until the dish comes up to temperature and the borax glaze becomes molten.

If you are using the Lowes MAPP/O2 rig (small yellow and red gas bottles) you are going to quickly find the O2 lasts less than 10 minutes and you will be spending a lot of money on red gas (O2) cylinders. If you are melting more than 2 OzT of gold, invest in a proper oxy/acetylene rig. Patience and practice is the key to melting powdered metals, as well as a properly prepared and insulated melting dish. For beginners, heating the dish from underneath is a good way to prevent blow away while observing the behavior of the gold at various stages of the melt. Melting is about heat lost and heat gained, not the intensity of the flame. You must add more heat than is lost, and you must add enough heat to heat the entire dish and the gold.

White fused silica dishes take longer to fully heat than the tan fireclay dishes, but the white ones are more durable and last for more melts. Fireclay dishes are more prone to crack if not slowly heated before applying borax glaze.



Steve
 
Thank you Steve.

That is pretty much exactly what I was trying to describe. I do not use the mapp/ oxy rig for the exact reason you stated.


I also don't use the torch head that make the little pointy crown like flame. The flame on those type torches look nice but they seem to take longer to build the heat needed and I know from experience that they use your gas faster.
I posted a picture some time back of the torch head I use. It is straight ( no igniter ) about 10 in long and has flutes on the intirror that resemble turbine blades that run nearly the full length of the torch. And for port holes at the base of the stem to pull atmospheric air into the gas stream. It would probably be best described as a type of venturi type air/fuel delivery.

Wish I could get this phone to post pictures, because I'm not nearly as good as Steve with my words.

Just follow Steve's excellent instructions and if you do choose to use mapp gas, don't cheep out on the torch head. It could very well cost you more in the long run.
 
I prefer a broad flame when melting my gold and a fine pointed flame when cleaning the final traces of impurities from the gold while it is molten. The focused pointed flame gives me more control over the molten blob of gold and allows me to stir the flux with the molten gold using the force of the focused pointed flame.

Steve
 
Ya what Steve says. :lol:
Ok I am going to go out on a limb here
First my disclaimer :don't try this unless you really
Don't care about ending up with your au on the
Walls and ceiling
***improper and unproven procedure*****
God I hope Harold doesn't break my limb :shock:

I have been glazing my melting dish exceptionally well
And bringing it to temp very slow for one reason
Moisture!!
When I have my au down to just the au I tip my
Beaker over around 150° and spray hcl in it to wash the au into my dish
let settle for 2 or 3 min. And somewhat decant
The dish then melt. Continued
 
Sometimes it is difficult to do the decant dish
If the gold doesn't want to settle quickly "I can always tell
The purity from that part"

I have had to develop my on methods as I am
Doing my lab work in my truck out in the field
(Literally) :lol:

I cannot dry my powders as they would definitely
blow away. (When I get my shop or lab I will
be happy to practice proper procedure 8)

New guys need to know this****I have detonated
a clay dish and pieces were found at every corner
luckily thanks to proper safety I had goggles on
and very little au******

I must say tho I still have my dish from 10+ processes
ago
Thanks Steyr223 rob
 
If you run the truck then turn it off when warm, you can dry it on the intake manifold.
 
g_axelsson said:
How about using silver powder as a cheap test metal? It is easily dissolved in nitric and cemented as a fine powder on copper. The easiest way is to have too little acid to dissolve all silver, then it is just to cement when the acid stops working.

/Göran
Click to expand...

I agree with this option - I have blown silver powder out of the melt dish before. Practicing on cement silver would be a great way to learn.
 

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