Can You Melt In Mold

[goldsilverpro]

There is no such thing as a 117 x 1 grain oblong cut. Grains are units of measure of weight, not lengths. You can not describe a cut as you have, so we have no idea what you really want.

Harold, I think he may have meant that there were 117 oblong depressions, each of which held 1 grain of gold. At least, that's the way I took it.

 

[shyknee]

A rolling mill is definitely the way that’s a great suggestion GSP's.
Nice 1
:lol:

ya then use one of these to make those rounds 8)

 

[Barren Realms 007]

There you go one pop = a grain and then have a 1 oz bar for them to lift and sell them the grns at $5.00 a pop. Capitolism at it's best. 8)

 

[Harold_V]

There is no such thing as a 117 x 1 grain oblong cut. Grains are units of measure of weight, not lengths. You can not describe a cut as you have, so we have no idea what you really want.

Harold, I think he may have meant that there were 117 oblong depressions, each of which held 1 grain of gold. At least, that's the way I took it.

Thanks, Chris. That does put a different slant on things.

The problem with his idea is that you and I both know that you simply can't pour gold to a specified weight. A mold small enough to yield a consistent diameter would have to be closed faced---like the book end molds you used to use for casting silver. To assume you could have a series of scratches (for lack of a better description) that got surface poured with the expected results of individual wires, or strips, is absurd. Gold simply won't cooperate, regardless of anyone's best attempts. If it was that easy, they could produce planchets for coins by pouring. They don't. The material is rolled to a predetermined thickness, then blanked with a punch and die, which guarantees size, weight and uniformity.

I know I sound like I'm trying to toss a bucket of water on this guy's barbeque, but there are certain absolutes that you simply must accept. This is one of them. If he has the inclination to pursue a given project, he'd be so much better served to observe discoveries that went before him instead of trying to re-engineer the wheel.

Harold

 

[Noxx]

Harold, I believe he's talking about this:

By experience, I can tell that it is impossible to cast 1 grain gold bars due to gold surface tension. Even with my 5 gram ingot mold, I can't get a nice finish on the top.

 

[Harold_V]

Harold, I believe he's talking about this:

By experience, I can tell that it is impossible to cast 1 grain gold bars due to gold surface tension. Even with my 5 gram ingot mold, I can't get a nice finish on the top.

The problem, of course, is that you can not pour so the molten gold ends up flush with the surface. You will pour too much, or not enough, so in spite of the individual cavities, the end result is failure. I dare say that it will also fail to fill the corners of the cavities.

An attempt to pour gold to a specific weight is wasted time. There are other means to achieve the desired end that are known to work reliably.

Unless one is trying to reinvent the wheel, there are times when one is best served to followed accepted convention. It may not be as interesting, but it's a sure way to achieve success.

Harold

 

[MargueriteMingorance]

Maybe he's a railroad modeller, and he wants real miniature gold ingots for a treasure car.

 

[Harold_V]

Maybe he's a railroad modeller, and he wants real miniature gold ingots for a treasure car.

I get the humor, but regardless of one's intentions, that simply doesn't work. When small bits of precious metals are desired, they are generally produced by dies, not molds.

Harold

 

[MargueriteMingorance]

Maybe he's a railroad modeller, and he wants real miniature gold ingots for a treasure car.

I get the humor, but regardless of one's intentions, that simply doesn't work. When small bits of precious metals are desired, they are generally produced by dies, not molds.

Harold

Yep, I can see the problem of controlling the pour on something that small. You'd have problems with voids in the corners, with over- or under-pouring, with keeping the mold sharp, and with getting your parts out. Some kind of stamp would be much better, either a die you can hit with a hammer, or some sort of punch or large pliers.

And one grain is tiny, it is 1/480th of an ounce (troy).

 

[ceritus]

The reason he wants to make one grain bars is because of http://www.ebay.com/itm/New-Capricorn-Zodiac-1-Grain-999-Pure-24kt-9999-Fine-Solid-Gold-Bullion-Bar-/220989320407?pt=LH_DefaultDomain_0&hash=item3373fd6cd7
and

http://www.ebay.com/itm/1-Grain-24k-AU-999-Solid-Gold-Bar-w-free-shipping-U-S-A-/110849573513?pt=LH_DefaultDomain_0&hash=item19cf264289

Saw some go for $8 with free shipping....


Gotta give the people what they want.

 

[MysticColby]

Fascinating stuff HAuC14 thanks for that.
Barren Realms I was not suggesting I did not believe what I have read on the forum. It is just that the sum of what has been written on graphite moulds is not clear and some things seem to suggest it is possible but not economical. Maybe if some one could point out why they sell graphite moulds for single grain bars in the first place? I am a learner and don’t know a lot about casting it is one of the things I am here to learn about. Many thanks.

I believe that the people who make these molds have never used them and just make them so they can charge more money to people who really want it to work.
I've tried to do what you suggest (on a 10-gram multicavity mold I made), and the top 1/8" of the mold had crumbled away into ash by the time the silver melted.
What might be possible is sintering. put 1 grain of powdered gold in each cavity, heat with torch for short time, powder will condense into glob of gold (this doesn't actually reach the melting temp, and it's more of a bead than bar, but it'll give you 117 beads of 1 grain each ) It only works if the amounts are small enough that they heat up much quicker than the mold.

 

[Abbarue]

I think that's the reason he wanted to know if the gold could be melted in the mold.
He probably was planing on putting fine gold dust into each little mold and then heating it in a furnace.
He did say he wanted to use a furnace and not a torch. So the whole mold gets heated at once.

Any way! I'm a new member here! I just signed up today, and wanted to say hello to everyone!
I'm wondering what's the best way to purify gold oxides?
Should they be treated with a chemical like HCl or should they be heated directly in a crucible.
I read that Digold trioxide decomposes at 150 C, but can this just be melted into a gold button in borax?

 

[Geo]

I think that's the reason he wanted to know if the gold could be melted in the mold.
He probably was planing on putting fine gold dust into each little mold and then heating it in a furnace.
He did say he wanted to use a furnace and not a torch. So the whole mold gets heated at once.

Any way! I'm a new member here! I just signed up today, and wanted to say hello to everyone!
I'm wondering what's the best way to purify gold oxides?
Should they be treated with a chemical like HCl or should they be heated directly in a crucible.
I read that Digold trioxide decomposes at 150 C, but can this just be melted into a gold button in borax?

gold oxide is soluble in hcl. gold oxide decomposes at a pretty low temperature so if it were mine, i would put it in solution and precipitate it as elemental gold before melting. im sure theres a simple redox method maybe like the silver reduction with sodium hydroxide and sugar. i dont know if sugar will work on gold oxide like it does for silver oxide but it sure would be quick and easy.

 

[Irons2]

I've 'Melted' Gold Oxide into a bead. One problem is if you heat it too quickly, the outgassing of Oxygen will blow particles all over your furnace. At a minimum, you will get tiny beads of Gold all over the inside surface of your crucible. It's better to warm it in a test tube to drive off the oxygen, then melt the resulting Gold Powder with a little borax for flux.
It does dissolve in HCl, which makes it handy for making Gold solutions of known concentration.

 

[Abbarue]

I've 'Melted' Gold Oxide into a bead. One problem is if you heat it too quickly, the outgassing of Oxygen will blow particles all over your furnace. At a minimum, you will get tiny beads of Gold all over the inside surface of your crucible. It's better to warm it in a test tube to drive off the oxygen, then melt the resulting Gold Powder with a little borax for flux.
It does dissolve in HCl, which makes it handy for making Gold solutions of known concentration.

Thanks!

The oxide dust is so fine I'm afraid It will blow all over if I take a torch to it, how can I best keep it together?

I'm from Canada and was wondering if someone knows a good place in Canada to order crucibles from?
Any other Canadians on this forum?

 

[richard_1]

You can of course get an induction gold melting machine which will heat your carbon mould by induction in an inert atmosphere saving the carbon wear. Weighing from powder and loading the mould would be very difficult at that size.