Non-Chemical Need some advice on Melting Gold _gasmeltfurnace_

[maynman1751]

Great 'heads up' guys, Thanks!!!!

 

[4metals]

I have always followed the rule that says never add anything to a melt that has completely melted. It is very common to scoop in more metal as a melt settles down in a crucible from the bottom melting but never when it is all molten.

Once, years ago, I was pouring copper into water making shot, the crucible was a #50 and it was in a cradle on a pivot pouring into a 100 gallon tank recessed in the floor. Sure enough, we poured too much too fast and it erupted, emptied the tank and thankfully only soaked us. The metal stayed in the tank. It turns out there was enough water to handle the quantity we were pouring but the water was stagnant, no circulation. When the water circulates it can distribute the heat faster. Without circulation the bottom water surrounding the hot copper turned to steam and exploded upward. Identical pours with circulation never had eruptions.

It is good to talk about these experiences, and sooner or later we all have them. It is a real success story to prevent someone from hurting themselves because they read about us talking about our own screw ups!

 

[Barren Realms 007]

I have always followed the rule that says never add anything to a melt that has completely melted. It is very common to scoop in more metal as a melt settles down in a crucible from the bottom melting but never when it is all molten.

Once, years ago, I was pouring copper into water making shot, the crucible was a #50 and it was in a cradle on a pivot pouring into a 100 gallon tank recessed in the floor. Sure enough, we poured too much too fast and it erupted, emptied the tank and thankfully only soaked us. The metal stayed in the tank. It turns out there was enough water to handle the quantity we were pouring but the water was stagnant, no circulation. When the water circulates it can distribute the heat faster. Without circulation the bottom water surrounding the hot copper turned to steam and exploded upward. Identical pours with circulation never had eruptions.

It is good to talk about these experiences, and sooner or later we all have them. It is a real success story to prevent someone from hurting themselves because they read about us talking about our own screw ups!

Ok that explains why mine did what it did. Mine was only a 2 gallon pot. I can only imagine the violent reaction of a 100 gallon tank.

 

[4metals]

This site may be interesting to anyone wanting to build the burners that Barren, Kurtak, and Palladium have had such success with.

http://metalcast.boorman.us/reil_1.html

This is the burner being tested by the author of the site in the link.

 

[Aeon13]

Thanks for the inputs guys!

Here is my update about my melting.

I melted a couple of buttons already. These are the ones the miners sold to me. These are elemental gold already melted into buttons but they used blower-charcoal set up. I remelted these buttons and had a good results for the first 3 buttons. I had a problem with the next buttons though. There is a black coating on top being formed (Am I correct that these are oxides being formed?). I read about the types of flames (reducing and oxidizing). I tried to minimize the air supply near the end of the melt to lessen oxygen being blown into the molten gold and thus finishing with a much yellow flame but still the black coating is present.I also tried to sprinkle borax on top of the molten gold. The coating is thin and will be removed if I file it but I am hesitant do it. Please comment/suggest/criticize.
Thanks guys and more power!

 

[ettran]

Kurt uses one that is the same size as mine and he doesn't seem to have any problems with it as far as I know. He was having some heat retention problems with it and had mentioned about building a new one and I suggested to him to close the hole in the top up to retain more of his heat but I haven't asked him if he tried it and if so if it helped him any.

Correct per the underlined above --- the heat retention problem is due to the fact that my furnace (my small one) has done soooo much work for me (including smelting - so we are talking "aggressive" flux involved) so the center hole in the lid has eroded & become "much" larger then it was when new so a lot of heat is being lost out the hole --- I am waiting for warmer temps so I can knock out the old refractory of the lid & re-pour a new lid --- I was considering just doing a repair (drill & pin around the inside of the hole & then do a refractory patch) but am afraid the patch wont really hold up well - so decided to wait & do a complete new pour of refractory

The heat retention problem is only a problem if I am trying to melt copper (with out adding air) - it still melts silver no problem

You will notice that my burner is set up so you can add compressed air (at the back of the burner) so I am actually able to over come the heat retention problem by increasing the burner heat out put by mixing 3 - 5 psi of compressed air --- so I am getting by with it as is until weather warms up enough so I can pour a new lid with a smaller center hole

Kurt

hi , where can I buy crucibles , ed.

 

[4metals]

Budget casting supply crucible page

http://www.budgetcastingsupply.com/Foundry-Crucibles-s/1830.htm

 

[4metals]

There is a black coating on top being formed (Am I correct that these are oxides being formed?).

The metal is not refined so you cannot expect to get oxide free melts every time. You could try to burn off some of the oxides while melting by using potassium nitrate on the molten metal but that will not work if the contamination is high.

I would melt with enough borax to cover the melt, oxides can dissolve in the borax and a pinch of potassium nitrate will help, then remove the beads when they solidify before the borax hardens around the bead and quench it in cold water. That should thermally shock off the excess borax, if not a dilute sulfuric soak will dissolve the borax.

 

[Smack]

I screwed up recently on the precipitation of gold in an A/R solution. I was in the process of dropping with SMB on a known amount (53g) of gold and was going to stop short of a full drop and decant the remaining gold bearing solution to keep drag down to a minimum but got distracted and added more SMB and as soon as it started to settle I noticed I just screwed up. You could clearly see (and I thought about taking a picture to show but didn't) a darker precipitate settling on top of a beautiful orangish gold precipitate.

 

[Aeon13]

There is a black coating on top being formed (Am I correct that these are oxides being formed?).

The metal is not refined so you cannot expect to get oxide free melts every time. You could try to burn off some of the oxides while melting by using potassium nitrate on the molten metal but that will not work if the contamination is high.

I would melt with enough borax to cover the melt, oxides can dissolve in the borax and a pinch of potassium nitrate will help, then remove the beads when they solidify before the borax hardens around the bead and quench it in cold water. That should thermally shock off the excess borax, if not a dilute sulfuric soak will dissolve the borax.

Thanks 4metals. I tried to add more borax that the button is submerged with it. I will try to find potassium nitrate and try to add. Is there a possibility that I am using the wrong type/mixture of air-gasoline combination? I am using an Air compressor- gasoline set up for melting.

Thanks again.
Mohammed

 

[Aeon13]

I screwed up recently on the precipitation of gold in an A/R solution. I was in the process of dropping with SMB on a known amount (53g) of gold and was going to stop short of a full drop and decant the remaining gold bearing solution to keep drag down to a minimum but got distracted and added more SMB and as soon as it started to settle I noticed I just screwed up. You could clearly see (and I thought about taking a picture to show but didn't) a darker precipitate settling on top of a beautiful orangish gold precipitate.

Thanks for sharing Smack. I am not into refining yet for now but I will eventually go there in the near future. This forum and you guys are big help. More power to all.

Mohammed

 

[Lou]

4metals,

You've melted platinum in this?

 

[4metals]

I assume you mean in the furnace I cast and posted the picture of?

Yes with oxygen injected into the chamber. The air is cut way back and the oxygen is fed into one of the valved gas feeds. It eats up oxygen like crazy, it gets hot enough to melt Pt but if you consider the oxygen usage it is not worth the price.

 

[kurtak]

Budget casting supply crucible page

http://www.budgetcastingsupply.com/Foundry-Crucibles-s/1830.htm

Although these crucibles from budget casting supply work I have found that they don't hold up quite as well as these :arrow: http://www.morganmms.com/produtos/cadinhos/salamander-super

The Morgan crucibles cost a little more but IMO are worth it in the extend life/use you get out of them - they are just a better crucible then the budget ones (again IMO)

I have been wanting to try Morgan's "ultra melt" crucibles as they are supposed to hold up even better to aggressive flux's - but have enough of the salamander super's to last me for awhile yet & so can't justify spending money on crucible at the moment

Kurt

 

[4metals]

I agree, Salamander's are better crucibles by far. But I have also learned here in the land of GRF that we go the full enchilada, from people wanting the best, to people wanting to make their own for free from rocks in their backyard! So, thanks to Kurt, you now have have a choice.

 

[Lou]

We order through Mifco

 

[jason_recliner]

Thanks 4metals. I tried to add more borax that the button is submerged with it. I will try to find potassium nitrate and try to add. Is there a possibility that I am using the wrong type/mixture of air-gasoline combination? I am using an Air compressor- gasoline set up for melting.

Thanks again.
Mohammed

As someone also struggling with melting, I've been following this thread keenly but I suspect this post became a little lost, being the final one on the previous page.
For anyone confused by the term "air-gasoline" I only presume it means what we would call LPG: or some country-specific ratio of propane + butane.

I am busting to hear any advice relating to oxidising/reducing flames. But back to Mohammed...

 

[Aeon13]

Thanks 4metals. I tried to add more borax that the button is submerged with it. I will try to find potassium nitrate and try to add. Is there a possibility that I am using the wrong type/mixture of air-gasoline combination? I am using an Air compressor- gasoline set up for melting.

Thanks again.
Mohammed

As someone also struggling with melting, I've been following this thread keenly but I suspect this post became a little lost, being the final one on the previous page.
For anyone confused by the term "air-gasoline" I only presume it means what we would call LPG: or some country-specific ratio of propane + butane.

I am busting to hear any advice relating to oxidising/reducing flames. But back to Mohammed...

Hello there jason. The "air-gasoline" I am using is gasoline that is liquid and is the one used in gasoline engines. I think propane and butane are different with gasoline? Forgive me, I'm not sure if we have same terms. I am from the Philippines and some terms used here in our place is hard to translate.

I have read Hoke's book,but I know I have to repeat again. I also read lots of topics here and gave me great help. Still, I am struggling now (which I suppose is natural),but I am hopeful that by further reading and asking from guys here in the forum I will be able to make some progress.

Acquiring materials(chemicals,melt dishes,torches,crucibles) that you guys use is also a struggle for me here. I am trying my best to find these chemicals. Until now, I am not able to find Sodium Metabisulfite-very easy one to buy there.

I have a small knowledge about the type of flame. I just know that Oxidizing flame is rich in oxygen and is not recommended for melting,. I read that neutral flame is the best in melting but is on the process of learning through experience how to make the correct mixture.

I hope to learn more from you guys.

Thank you.

Mohammed

 

[jason_recliner]

The fact that you are reading, and actively willing to learn means that the majority of people here do their utmost to help you. It's only when one shows laziness and a lack of willingness to acquire knowledge, that they are shunned. I am also still a minor, still gleaning knowledge from the edges.

Sodium Metabisulfite Na₂S₂O₅ is commonly used as a steriliser, available at brewing shops, at least in AU/US/UK. It would be worth investigating that source in Filo as well. My local brew shop isn't even sure their sodium met from potassium met (they were busy re-labelling it during my last visit) - K2S2O5 should work too, in theory you would just need a bit more of it.

The idea of using automotive gasoline / petrol, kind of scares me somewhat. There's an awful lot to go wrong. Gas (as in literally, the physical state of gas) is much easier to control than a liquid that is on fire. I say that as a former firefighter. This is why I presumed when you said air/gas that you probably (or hopefully) meant barbecue type LPG cylinders? Other than that, I can't speak for the process. Still playing with it myself, I'm behind most regulars here when it comes to melting. That's why I'm also following this thread so tightly.

 

[Aeon13]

The fact that you are reading, and actively willing to learn means that the majority of people here do their utmost to help you. It's only when one shows laziness and a lack of willingness to acquire knowledge, that they are shunned. I am also still a minor, still gleaning knowledge from the edges.

Sodium Metabisulfite Na₂S₂O₅ is commonly used as a steriliser, available at brewing shops, at least in AU/US/UK. It would be worth investigating that source in Filo as well. My local brew shop isn't even sure their sodium met from potassium met (they were busy re-labelling it during my last visit) - K2S2O5 should work too, in theory you would just need a bit more of it.

The idea of using automotive gasoline / petrol, kind of scares me somewhat. There's an awful lot to go wrong. Gas (as in literally, the physical state of gas) is much easier to control than a liquid that is on fire. I say that as a former firefighter. This is why I presumed when you said air/gas that you probably (or hopefully) meant barbecue type LPG cylinders? Other than that, I can't speak for the process. Still playing with it myself, I'm behind most regulars here when it comes to melting. That's why I'm also following this thread so tightly.

You are right jason. many guys here including you are very helpful and accommodating. I learned a lot here in the forum for only a couple of months. I could only imagine what can I acquire after a year or two here.

As for the SMB, I asked a reagent dealer and they told me they will contact me if it is available.

This method of air-gasoline is being used here for some time already. I think it has the same principle because the air compressor is connected to a tank which contains a small amount of gasoline(about two cups) and this liquid gasoline evaporates the gas state which I think is the ones being pumped out together with air to the torch. I will upload a picture of this set up tomorrow for you guys to comment/suggest.

I'm a super newbie compared to you guys though. :mrgreen: But I'm willing to learn from the best.

Thanks again.

Mohammed