Saturn industries/graphitesupplies.com(be careful)

[goldenchild]

First I would just like to say that I have ordered from http://wwww.graphitesupplies.com and they make good molds. However, I'm now having to explain to a client who has sent me two custom molds made by Saturn Industries http://www.saturnedm.com , why pouring a half ounce of gold (15.5g) into a mold with a cavity the size of a quarter will not work. All the veterans can stop reading here but I will explain for those that don't know why.

Gold does not act like water when it is poured. It has a great amount of surface tension and "freezes" as it's being poured. And without a special mold and melting setup, and short of hammering or rolling your gold, it will never have a flat surface. Commercial gold coins are stamped out of flat sheets of gold (that have been rolled themselves) with machines that exert tons of pressure per punch.

I don't know if Saturn Industries owns Graphite Supplies or vice versa but they are working. My client says that he was very specific in what he asked for in the mold. I feel like Saturn Industries should have been professional enough to know and explain that pouring a half ounce of gold into a quarter sized cavity would not work. After all they are in the business of making measurements for making molds accommodate given amounts of metals. Not saying that these companies are bad but just make sure you do YOUR research and be VERY specific in what you need.

 

[Jimmy]

When pouring metals with high surface tension you need high head pressures on the sprur and risers too.
Gold is more thermally conductive than aluminum. Not quite as much as copper so it needs larg sprues when you pour small pieces. They lose their heat quickly and solidify. Gateing is very important.

Im by no means an expert on gold. Mainly Aluminum and copper alloys.

 

[Lou]

If your mold is hot enough, you will be able to pull it off.

It will be tough. You may be able to do it in a controlled atmosphere kiln.

 

[MysticColby]

a cold mold will indeed give the least desirable results. a hot mold will still result in a button no matter the temperature. Something like this:

As the size of the mold gets bigger, it will be closer to this:

If you want a rectangle or cube, you must use a 2-part mold (or huge rollers/punches/pressures)

 

[Canvasman34]

Hello to all,
I am Canvasman34, I manufacture P.M. melting and pouring supplies as well as make youtube videos on the various items I make and how to use them.
Surface tension....isn't it wonderful. I want a flat ingot and all i can get is a loaf of bread looking ingot.
As for Saturn Industris /PMC supplies, they are good folks selling allot on ebay and other world markets. As to molds, I make allot of graphite molds, and the hardest part is making the ingot come out at the right weight and look good. I made my first mold the other day that i sold as "1 Ozt .999 silver/ 2 ozt. 24K gold". The determining factor is the specific gravity of the two different metals. The specific gravity of .999 fine silver is 10.5. The specific gravity of gold (24K cast) is 19.23, not a two to one ratio. Using surface tension to the mold makers advantage, you can overfill one or under fill the other and get close. You will see bread loaf tops or rounded corners. I buy my competitors molds just to check them out. The rule of thumb seems to be to over cut the depth so a "Ounce" will fit for sure. I bought a 5 ounce KitKat off a seller, made a sprue plate and cast it as a "Flat Back" ingot and it weighed 6.75 ounces.
One of the other factors is we cut the graphite with a tapered end mill. For small ingots I use a .125" diameter with a 1 degree taper. On the larger molds I cut with .250" diameter at 5 degree taper. This is so when the ingot cools, it will come out of the mold. The tapered sides and rounded and tapered corners prevents the calculating the desired an ingot cavity will produce based on cubic volume of the mold cavity. I made an Excel spreadsheet that gets really close.

 

[jonn]

Welcome to the forum canvasman. Send me a pm if you need graphite blocks. I've got some for sale.

 

[Palladium]

Welcome to the forum sir.