Non-Chemical Hi all, a few questions

[Barren Realms 007]

Oz, does it do any harm to the metal other than making it brittle? I use an acetylene tourch with a turbo tip set up. Does it do any damage that would effect the sale of a nugget?

Platinum can become brittle even if pure, if it is melted with an acetylene torch.

 

[Oz]

Acetylene flames tend to be dirty with carbon and it is this carbon that contaminates the platinum that makes it brittle.

Most platinum buyers would prefer to buy platinum in sponge form since it is easier to put into solution for checking purity or making compounds. Ever try taking a decent size platinum button into AR even under heat? Set aside a good bit of your day.

As to a brittle button affecting sale value, it may if part of how they are judging the purity of your platinum is its ductility. Very slight contamination of other elements affects the normally malleable nature of pure platinum.

 

[Harold_V]

Thanks for clearing that up for me. I take it that the three glass jars are diffrent states of platinum.

Correct. Left one is the platinum as recovered with ammonium chloride. Middle one is the calcined material (platinum sponge) and the right side is a melted button.

I'v seen it discussed about gold craking on the edges because of work stress. Does platinum do this as well?

I did no annealing with the coil in the picture---but the slightest contamination can cause platinum to "alligator". It can be caused by carbides that form when melting the platinum (read what Oz said), or by traces of other elements, primarily silver.

And that is a nice looking coil, I guesss you rolled this yourself?

Yes, with the set of power rolls I used to own. When I retired and moved to Washington, they were sold to one of my customers. The platinum coil was my first attempt at refining platinum.

For the sake of clarity, the button shown in the picture (front, center) is slightly larger than a troy ounce, and, like the coil, is still in my possession.

Harold

 

[Barren Realms 007]

Platinum can become brittle even if pure, if it is melted with an acetylene torch.

Ok that brings up a couple of questions then.

Does this mean you can't use an oxy/acet tourch to melt platinum?

Does an oxy/acet tourch get hot enough to burn the carbon and not contaminate the platinum?

If oxy/acet is ok to use here is my next question. The acet tourch I use has a tip like a brazing tip on an oxy/acet but bigger around(size of pinky finger). When it is opened up the flame is close to the tip like an axy/acet barzing tip. This burns hot enough to silver solder up to 1" copper for this tip. A lot hotter than a mapp gas tourch too( I use both of them on a regular basis). With it burning at these temps would it rule out competently using it to melt platinum with out contaminating it just because it is acet ?

 

[Barren Realms 007]

Thanks for clearing that up for me. I take it that the three glass jars are diffrent states of platinum.

Correct. Left one is the platinum as recovered with ammonium chloride. Middle one is the calcined material (platinum sponge) and the right side is a melted button.

I'v seen it discussed about gold craking on the edges because of work stress. Does platinum do this as well?

I did no annealing with the coil in the picture---but the slightest contamination can cause platinum to "alligator". It can be caused by carbides that form when melting the platinum (read what Oz said), or by traces of other elements, primarily silver.

And that is a nice looking coil, I guesss you rolled this yourself?

Yes, with the set of power rolls I used to own. When I retired and moved to Washington, they were sold to one of my customers. The platinum coil was my first attempt at refining platinum.

For the sake of clarity, the button shown in the picture (front, center) is slightly larger than a troy ounce, and, like the coil, is still in my possession.

Harold

All 3 of those look nice Harold. The roll looks very good. Do you remeber how many times you ran it thru the press? I take it that it was a button when you started with it.

And the carbides that form that can be from carbon or any other elemental contaminant in the atmosphere then. Ok am I correct in understanding that it is recomended that platinum should be melted in a vacume? Or can an inert gas like argon be injected into a crucible to get a similar desired effect?

Sorry about getting off thread. :roll:

 

[Harold_V]

All 3 of those look nice Harold. The roll looks very good. Do you remeber how many times you ran it thru the press? I take it that it was a button when you started with it.

Correct. I don't recall the actual weight now, but it was in the neighborhood of a third of an ounce. Needless to say, it started out as a button. As a result, it was run through the rolls several times. That's normal for rolling. Its not accomplished with single passes, but a series of repetitive passes, each one making the material thinner than the last. Perhaps a half dozen passes total for the strip.

The material isn't flawless---there's a little open place or two where there was a low spot in the button, and there's a hint of aligatoring on the very edges. A sign that the platinum was not perfectly clean, nor did I expect it was. It was simply my first experience, and I wanted to explore how it turned out.

And the carbides that form that can be from carbon or any other elemental contaminant in the atmosphere then. Ok am I correct in understanding that it is recomended that platinum should be melted in a vacume? Or can an inert gas like argon be injected into a crucible to get a similar desired effect?

What is recommended is a hydrogen torch, which eliminates introduced carbon. An inert atmosphere certainly wouldn't hurt, but isn't a requirement.
I melted all of my platinum with a torch, using natural gas, or oxy/acet. You can get away with that setup so long as you use an oxidizing flame instead of a reducing flame. It's just the opposite of what you'd want when melting alloy gold or silver, but it also yields the hottest flame, which is important when melting platinum. It's pretty hard to melt much more than an ounce and achieve good results with a torch. Induction melting is the way to go, but few have that luxury. Even fewer have enough platinum to make that a concern. I accumulated only about 75 ounces of platinum in my more than 20 years of refining, and I handled a considerable amount of dental alloy in my years.

Harold

 

[Barren Realms 007]

What supprised me about the platinum you rolled out is that it dosen't look like it spread out sideways just length wise. Did you do somethign to it to make it spread that way?

 

[goldsilverpro]

What supprised me about the platinum you rolled out is that it dosen't look like it spread out sideways just length wise. Did you do somethign to it to make it spread that way?

That's the way it always works when you put metal through a set of rolls.

 

[Harold_V]

What supprised me about the platinum you rolled out is that it dosen't look like it spread out sideways just length wise. Did you do somethign to it to make it spread that way?

That's the way it always works when you put metal through a set of rolls.

Yep! If you want it wider, you must start with a wider button or ingot, or you must send it through the roles to widen it to the desired width, with a little excess. It is then rolled @ 90° to the width, to the desired thickness. From this, you can conclude that the button from which the ribbon was rolled was roughly the size of the ribbon. It tapers on each end, just as the button diminished in width at each end.

Harold
Edit:
It's fun to watch the rolling process. The outgoing metal is moving at a faster rate than the ingoing metal. The metal is displaced in the process of rolling, making the ribbon ever longer as it gets thinner.