Gold Conductor Paste - Please Advise

[NeoRock]

I would really appreciate some guidance, novice here. I have taken good pictures which I am attaching to illustrate my conundrum. Long story short, after helping my cousin with some things, (who is now in Africa filming wildlife for 6 months, so I can’t ask him anything) - I was left with what he told me was “Gold Conductor Paste.” - PLS SEE PIC A
He was using it off label for something specific, but I believe he said, it was generally used for “printing conductor lines in electronic boards.” I received the conductor paste in a small plastic tube & some more in a “zip lock style” sandwich bag.
So I’ve been reading the forums & watching videos, trying to find out the best way to melt & sell it. I left it in drawer with a Desiccant bag which dried it out and I was able to scrape out most of it (about 30g), now in a “dirt” kind of consistency. After scraping most of the gold paste out….I also still have a decent amount of left over gold paste stuck to the plastic tube and plastic bag, - PLS SEE PIC B - any simple way to separate the gold from the plastic?? (its very soft plastic).

I was told the paste is more than 22K, close to pure, that it has very miniscule amounts of additives which, in the normal manufacturing process of using it for circuit board printing, are designed to burn off leaving just gold in the normal circuit board…. I had a gold tester kit, so I checked with the 22K solution - PLS SEE PIC D. PIC D is the gold with Nitric & Muriatic Acid on it - I got absolutely zero reaction. So I read the forums and watched a bunch of videos for a couple of weeks...and figured it would be fun to learn...and melt so I built a little “can” foundry off one of the youtube vids and have some map gas going to it - SEE PIC E & PIC F…..PIC F is image of my graphite crucible inside the can foundry. The sides of the can (the “insulation” is made of equal parts, “plaster of paris” and sand...and of course a bit of water….dried for 2 days. ****** Please note...Obviously I am doing the actual melting attempt outside in ventilated area but took the pictures inside for better clarity*****

I also got some borax to get out any impurities (which I throw in a pinch while the flame was on). I am only using a bit of the gold (about size of a pomegranate seed) until I can see it melt & know I am doing it right….then I will do the bulk.
However, I am not sure what I am doing wrong….as it seems never to get to the melting point. I just end up getting a much drier version of the “dirt” consistency but with yellow colored gold highlights -
So I have a couple of questions…much obliged to you guys for any help...Thank you.

1)Any advice on why I am not getting to the melting point, especially since on my test runs, I am only trying to melt a tiny amount (about size of a pomegranate seed)??
2) Is there an easy method to separate the Left Over gold paste stuck to the walls of the plastic tube & plastic bag that I can’t scrape out?
3)Also, any safety concerns with my setup?
4)Anyone know if I can just sell it in the “dirt” consistency or would I lose too much value?
5)Any additional suggestions, much much appreciated.

Thank you very much folks, my apologies for the lengthy post, just wanted to be thorough. If anything needs to be clarified, please let me know.

Much Obliged,
Mark


p.s. the post keeps reversing my image order....if you hover with the mouse over the image, the name will appear as its referenced above.

 

[butcher]

You could melt the plastic and glass if you wish along with the powder.

I can see the furnace has fuel gas, but where is it getting the air or oxygen to burn the fuel and provide the heat needed to melt the gold?

It may work better just using the torch (with its gas/air mixing tip) and melt the gold in the dish directly without the furnace.

 

[anachronism]

Yes completely concur- that torch is good enough to melt a small amount without making it into a furnace. I used to be able to melt up to an ounce with a mapp gas torch.

 

[NeoRock]

You could melt the plastic and glass if you wish along with the powder.

I can see the furnace has fuel gas, but where is it getting the air or oxygen to burn the fuel and provide the heat needed to melt the gold?

It may work better just using the torch (with its gas/air mixing tip) and melt the gold in the dish directly without the furnace.

Thank you for your reply, much appreciated. Please excuse my ignorance as I am very much a novice. The video I was following did not have another "hole" for oxygen...but now that you say it, that makes perfect sense. Obviously, more oxygen, higher burning. Should I just make a hold on the other side of the can??

Also, you said "you could melt the plastic along with the powder".... would that not contaminate the gold with the plastic, or does it burn off completely?

And initially I did try just using the torch portion of my setup, but even trying to melt a "pomegranate seed size" amount, wouldn't happen. I had the gold in a crucible and had the torch on it for more than 5 minutes but all I (see image attached) got was a harder spec, with yellow highlights on it. I am also attaching the data sheet for the actual paste...

 

[NeoRock]

Yes completely concur- that torch is good enough to melt a small amount without making it into a furnace. I used to be able to melt up to an ounce with a mapp gas torch.

Thank you anachronism, I appreciate it. I did try the mapp gas torch initially, (three attempts) but even trying to melt a tiny spec of it inside a crucible...didn't work for. The result was (attached images). Please keep in mind this was torching it in excess of 5 minutes. What I also kept running into was the "blue flame" of the torch would stutter after a couple of minutes & would turn into a regular yellow flame. I would get it going again, just not sure why it kept happening.... The map gas is almost finished, but I bought another one....

Any thoughts?
Thank you

 

[anachronism]

I think it's the bonding agent that's causing you the problem.

Remember that it's fired to achieve the bond. You need a solvent for the bonding agent to free up the gold.

Edit for typo.

 

[NeoRock]

I think it's the bonding agent that's causing you the problem.

Remember that it's fired to achieve the bond. You need a solvent for the bonding agent to free up the gold.

Edit for typo.

I think you are spot on...I was told it was mostly pure, but had some additives. Normally, this paste would be used to print conductor lines on a substrate and the substrate run through a very long furnace. As it proceeded (very slowly) from one end to the other end of the furnace (I believe they said like half an hour), while it was in there...the additives would burn off, leaving the "cured" gold as "conductor lines." --- see attached image, its the end result of what this paste was originally intended for

With that in mind, shouldn't the torch do the same and "burn off the additives?"

Otherwise, I am not sure what the "bonding agent" is, any ides on figuring out what solvent to use?
Originally, I didn't even want the stuff, I was just happy to help my cuz...but he insisted... as a "thank you" as he was leaving to Africa. I then almost throw it out, as I didn't know what to do with it...but then saw this forum & also some videos....Thank you very much....

Edit to add image

 

[butcher]

The torch head itself is designed to pull in air mix it with fuel at the nozzle giving you the hot blue flame (oxidizing flame), starved of air (oxygen) the fuel burns with a cool (reducing) yellow flame.

If the flame from the torch is burning yellow it will not be hot enough.
Some torches use screens in the torch head that can get corroded or fouled from the misuse, you might check to see if it has a screen that needs to be cleaned.

The furnace might work if you can get the torch head into the hole you have already, where the torch head can pull its own air, you want a blue flame in the furnace...

The torch with its blue flame is hot enough to burn off the plastic, melt the glass into slag, and melt the gold.
But we also have to consider other factors:
How much does it take to heat the melting dish?
How much heat is wasted trying to keep the dish hot cherry red hot?
What is radiating heat away from the dish, say if the crucible or melting dish was sitting on a big heat sink like a thick plate of copper the copper will pull heat away from the dish-- if the melting dish was in the air which would not be as much of a heat sink we are not using up fuel just to try and get the gold in the dish hot enough...
Even the crucible itself or melting dish is a heat sink that can pull away or consume heat that would otherwise be used to melt the gold.

You can boil water in a paper cup over an open fire, where the water is a heat sink for the cup...


I cannot see where you would need any solvent to melt the gold to metal.
My guess is the solvent is most likely used to thin the paste before firing.

I am unsure of the binding agent, but from what I can read of the datasheet they are firing these traces at 850 degrees C for 30 minutes on certain substrates like alumina, which is below the melting point of gold (1064 deg C), so they are not melting gold into a gold metal wire or trace...

The bonding agent may become part of the electrically conductive trace after firing (I do not know) can you get the MSDS sheet to figure out what the binding agent is, and one for what the solvent is?

You may have to flux melt out the boding agent, firing below the melting point of gold you can make a blob of gold along with its binder.

 

[g_axelsson]

To quote Harold... Incinerate!

Just incinerate any plastic with gold at it. You will be left with a little bit of ash and the gold powder. The binder in the paste will also burn away when you melt it, there's no need to dissolve the binder.

Göran

 

[snoman701]

It’s likely a polymer to aid in the screen printing. Needs to be thixotropic to go through the screen.

You don’t want to try to use solvents....you’ll just make a mess. Lay it out thin and fire it.


Sent from my iPhone using Tapatalk

 

[NeoRock]

The torch head itself is designed to pull in air mix it with fuel at the nozzle giving you the hot blue flame (oxidizing flame), starved of air (oxygen) the fuel burns with a cool (reducing) yellow flame.

If the flame from the torch is burning yellow it will not be hot enough.
Some torches use screens in the torch head that can get corroded or fouled from the misuse, you might check to see if it has a screen that needs to be cleaned.

The furnace might work if you can get the torch head into the hole you have already, where the torch head can pull its own air, you want a blue flame in the furnace...

The torch with its blue flame is hot enough to burn off the plastic, melt the glass into slag, and melt the gold.
But we also have to consider other factors:
How much does it take to heat the melting dish?
How much heat is wasted trying to keep the dish hot cherry red hot?
What is radiating heat away from the dish, say if the crucible or melting dish was sitting on a big heat sink like a thick plate of copper the copper will pull heat away from the dish-- if the melting dish was in the air which would not be as much of a heat sink we are not using up fuel just to try and get the gold in the dish hot enough...
Even the crucible itself or melting dish is a heat sink that can pull away or consume heat that would otherwise be used to melt the gold.

You can boil water in a paper cup over an open fire, where the water is a heat sink for the cup...


I cannot see where you would need any solvent to melt the gold to metal.
My guess is the solvent is most likely used to thin the paste before firing.

I am unsure of the binding agent, but from what I can read of the datasheet they are firing these traces at 850 degrees C for 30 minutes on certain substrates like alumina, which is below the melting point of gold (1064 deg C), so they are not melting gold into a gold metal wire or trace...

The bonding agent may become part of the electrically conductive trace after firing (I do not know) can you get the MSDS sheet to figure out what the binding agent is, and one for what the solvent is?

You may have to flux melt out the boding agent, firing below the melting point of gold you can make a blob of gold along with its binder.

Butcher, thank you very much. That was really informative…. I learned a lot from your post and you touched on a couple of points that occurred to me after I had already posted. And thank you for being so thorough, that was great ...appreciate your time.

There is a “3 point shape C” inside the torch head, (see image) Does it seem good enough to you?

My first try was blasting a spec of the gold directly with the torch. However, after 2 or 3 minutes it would turn into the “yellow” flame….Exactly as you mentioned, then couple of seconds later, it would go out “stuttering” (even though I was holding it very steady). Once I setup the furnace pictured above, the flame stayed on…but again, never to melt.
Your description of “heat loss” in respect to the various items “acting” as heat sinks may have unearthed the issue. I realized I had the crucible sitting on the bottom of the furnace...it was even sitting a little lower than hole where the gas was coming in (attached image). From what you said, its better if the crucible is lifted a bit in the air, correct?

In respect to solvents, I do remember him mentioning when the gold paste was too thick, they would add a couple of drops of some Dupont thinner (referenced in the datasheet above) to get the viscosity to a workable level, then print, then fire it…as once again you impressively, already knew. Also, they did only use micron amounts of the paste on each alumina, so not sure if that made the firing process much easier.
I filled out a “MSDS” request form on Dupont site for the paste & thinning agent as googling for over an hour, I couldn’t find them anywhere. Hopefully, they send it & I’ll post here.

I got some Borax from amazon (also attached image). Vids I watched said to use borax to get impurities out. Should I use this at all or is the "flux melting" you mentioned different?
Also, I saw canisters of oxygen at home depot. If I made a hole on the other side & had oxygen going in, would this dramatically increase the temperature & make things faster or not necessary?? Thought I had another can, but I am almost out of the mapgas. I do have 2 big cans of propane which I know has somewhat lower burning temp... will the propane suffice?

Again, thank you very much, really do appreciate your time...& pickin your brain

 

[butcher]

Even for the same gas, not all torch heads or brands are alike, some are just better quality than others, some will burn much hotter than other brands on the same gas, but if working properly will melt gold.

Propane/air is will melt gold in the proper setup, but it is more difficult, it is not as hot as propane oxygen or Mapp gas, acetylene/oxygen...

You might try taking your torch head apart and cleaning it.

You do not need a furnace to melt gold.
I like the small ceramic melting dishes, they work good with a good Mapp gas torch.

You may not need the borax or flux agents since you have a graphite crucible, the borax flux can help lower the melting temperature and help the melt flow, or raise the viscosity of the melt so the metals combine better in the melt, it would also provide some glass to cover the melt and help to keep it from sticking to a ceramic melting dish.
In a flux melt, it is a part of the flux recipe used to control the chemistry going on in the melt.

With a ceramic melting dish, and melting pure gold we will sprinkle just a little borax on the red hot dish, just to coat it with molten glass so the molten metal will not stick to the dish and the molten can be poured from the dish.

In a flux melt, we use much more borax is used along with other flux components like oxidizing or reducing agents...
When using graphite melting fairly pure gold the borax is not needed to keep the gold from sticking.

As far as modifying your furnace with another hole and adding oxygen, you could make it into a cute little bomb if you do not know what you were doing. I would mix gas and air before it enters the furnace.

 

[anachronism]

Or the OP could just take the KISS approach instead of complicating it. 8) 8)

Jon

 

[butcher]

Propane or Mapp gas, like oxygen, can be a liquid or gas, with the bottled fuel gas turning the torch (fuel bottle) upside down can feed liquid to the torch instead of gaseous fuel, thus giving you more liquid to the orifice and less of the more volatile fuel gases, resulting in a lack of air, cooler burn, and a yellow flame-spitting or sputtering to stay lit...

 

[Martijn]

I believe for a furnace like that to work well, the gas/flame/torch inlet should be ofset from the center, creating a vortex of flames around the crucible in the center. This distributes the heat a lot better, increasing the temerature. your's looks like it is aimed exactly to the center. It could make a lot of difference.

 

[anachronism]

I believe for a furnace like that to work well, the gas/flame/torch inlet should be ofset from the center, creating a vortex of flames around the crucible in the center. This distributes the heat a lot better, increasing the temerature. your's looks like it is aimed exactly to the center. It could make a lot of difference.

The issue is that the Mapp gas is running at not that much higher a temperature than the melting point of gold. The nozzle on the bottle is designed to get the most efficiency out of that gas. Once you start altering things and introducing a whole host of other variables it's only decreasing in efficiency.

 

[butcher]

View attachment melt.rtf
some pictures

glazing melting dish
https://www.youtube.com/watch?v=NRHh_fqfQoE

Martijn, is correct in his assessment of a well-built furnace design. He was not speaking about modifying the torch but how the fire burns around the crucible inside the furnace...

 

[Martijn]

I believe for a furnace like that to work well, the gas/flame/torch inlet should be ofset from the center, creating a vortex of flames around the crucible in the center. This distributes the heat a lot better, increasing the temerature. your's looks like it is aimed exactly to the center. It could make a lot of difference.

The issue is that the Mapp gas is running at not that much higher a temperature than the melting point of gold. The nozzle on the bottle is designed to get the most efficiency out of that gas. Once you start altering things and introducing a whole host of other variables it's only decreasing in efficiency.

Point taken. It just caught my eye. If he should use propane with oxygen in the future to run this furnace, the crucilbe would mostly get heated from one side. Thats not ideal and could wear the crucilbe from one side faster.

 

[butcher]

I cannot say what the binders are in the conductive paste, I have never worked with them.

But I used to make my own paste solders of lead or silver composition, and low-temperature paste solders you can solder copper wires with a match.

The conductive pastes have a low melting point, they are fused to aluminas, or glass or some other substrate and need to be fire below the melting point of the material the conductive paste is fired upon.

the Binders can be part of the trace after firing (at these lower temperatures) say carbon for changing the resistance of the trace or wire, metal oxide powders like copper or cadmium, glass binders, metal inorganics, thermoplastics, polyvinyls, and polymers, resins...

I believe most of these organic binding agents would burn off or slag out at the melting temperature of gold, especially with a conductive paste that has a high gold content (for low resistance after firing), but then it also depends on the binder's organic or metallic composition ...

 

[Lou]

Usually binders are glycols, some ketone solvents, and carboxymethylcellulose.