# Platinum mold question



## goldandsilver123 (Sep 29, 2015)

Hello,

I just found here in the forum, that one can make jewelry directly by melting type S thermocouple.

My question is: where do I pour the molten platinum/rhodium alloy?

Since my iron molds would melt at platinum melting temperature.

my molds:



Thanks!


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## MarcoP (Sep 30, 2015)

Hi, if you want to make jewels shouldn't you shot the metal directly inside a crucibles (lost wax).


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## goldandsilver123 (Sep 30, 2015)

Not necessary, that process is used with large quantitys of material, we do small bench work.

To make a solitary for example, the metal is poured on the right mold, than it's rolled to make a small square wire, cut to size, bend, solder, etc, etc...

I'm just lost on what do I pour the platinum... I could improvise with a graphite brick, but don't know if platinum is compatible with graphite ( I know you cannot melt it in a graphite crucible).
Thanks!


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## Lou (Sep 30, 2015)

The molds for platinum are two or three piece book molds of solid copper. The platinum cools so quickly it does not stick.

Lou


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## goldandsilver123 (Sep 30, 2015)

Lou said:


> The molds for platinum are two or three piece book molds of solid copper. The platinum cools so quickly it does not stick.
> 
> Lou



Seriously?? That's awesome and I would never think of that!! =)

I never saw one made in copper for sale, I will have to make one

Thanks!


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## GotTheBug (Sep 30, 2015)

I was going to say graphite mold, never thought of copper either. One more nugget for my noggin.


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## allenp (Oct 7, 2015)

Make sure that the copper mold is very warm(free of anything that can volatilize) before you cast - otherwise you will be picking Platinum off the ceiling.


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## MarcoP (Oct 7, 2015)

Some CPU heat sinks have a solid copper core, could it be used for tiny lots, maybe up to 5gr? Interesting the fact there is no need for a mold release agent.

Marco


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## justinhcase (Oct 7, 2015)

Do not the dissolved gases from the atmosphere muck up the casting.
http://www.alibaba.com/product-detail/AX-MAX1-Vacuum-Casting-Machine-with_1580186789.html?spm=a2700.7724857.29.135.cNhWfD


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## Lou (Oct 7, 2015)

Typically, put the book mold in assay oven at 250 C for an hour. Top of the mold is sprayed with boron nitride mold release. This isn't for release, it's so you can see the hole to pour in. High intensity xenon spot light helps see where you're going when you're pouring 15 kg of something very heavy and very bright.

As for casting small amounts of Pt, easier said than done. Freezes as soon as heat is off


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## goldandsilver123 (Oct 7, 2015)

I was just reviewing this video by chance: https://www.youtube.com/watch?v=X09zSQSUXDk 

I think they used a water cooled 2 part copper mold (you can see the reddish color when they open the mold), for that amount of platinum I think water cooling is a must...

I wouldn't have noticed if Lou didn't commented


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## Research135 (Oct 12, 2015)

goldandsilver123 said:


> I was just reviewing this video by chance: https://www.youtube.com/watch?v=X09zSQSUXDk
> 
> I think they used a water cooled 2 part copper mold (you can see the reddish color when they open the mold), for that amount of platinum I think water cooling is a must...
> 
> I wouldn't have noticed if Lou didn't commented


Very nice video!. They seem to be a large processor. Did you notice in the induction furnace the crucible refractory?. What material is that?.


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## Lou (Oct 12, 2015)

zircon


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## Research135 (Oct 13, 2015)

Thanks Lou. You probably meant Zirconia. 
I also noticed sheets of a paper-like material in the trays when they calcined the yellow powder. The material was gone after they pulled the trays with the calcined sponge from the tube furnaces. What are those sheets?.


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## Lou (Oct 13, 2015)

No, I meant zircon. Geez. As in zircon sand, as in zirconium silicate. That's what gets packed around the zirconia crucible. Or should I say yttria-stabiized zirconia crucible? You seem to be a double guesser/arm chair speculator extraordinaire. 

As for the sheets--no idea. We use big sheets of ashless filter paper between that and the silica boat that is covered in zircon wash coat with MgO final coat.


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## g_axelsson (Oct 13, 2015)

Is this enough for a crucible to melt my meager amount of platinum? :mrgreen: 







A 2 cm zircon crystal I have in my rock collection.

Göran


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## Research135 (Oct 13, 2015)

Thanks.


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## goldandsilver123 (Nov 19, 2016)

I finally got to make something out of platinum, thanks Lou!

I made the copper mold from 5 pieces of copper bar held together by a screw with one side free to adjust the size.

I heated the mold in a muffle oven to 250 °C.




O2 LPG torch melt:









In the second time, I got this black spot under the bar, I think it's because the oxide layer was flaking and I didn't see it... anyhow HCl got rid of it


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## Lou (Dec 16, 2016)

Wow, I jsut saw this.

Really great work!


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