andremajic
10-20-2013, 02:07 PM
Ok, so this is called cuttlefish casting. It's an ancient technique used by the egyptians and greeks to cast jewelry and other objects.
I'm using this technique with a cuttlefish shell that is available at pet stores. They're used by parakeets to chew on. Next time you're buying some ground walnut shells, pick up a few. They're cheap.
Cut it in half with a hacksaw, then start sanding down the soft side on a piece of 80 grit sandpaper on a flat surface.
84822
Get your object you're trying to duplicate and press it half way into one side of your shell, it's pretty soft, but can break if you put too much pressure, so easy does it. (You can also carve freestyle into it if you wanted to, but I'm not that great of an artist.) Next get some small ball bearings and smoosh them into the mould half way as well. These will be used as reference points when you rejoin the halves.
84824
Next, carefully line up the halves and smoosh them together until you have no air gap between the two. This part is where you're most likely to crack the mould if you're not careful. Take them apart, and voila! (you can see the upper left corner is cracked. It will still be wrapped with wire to keep it together, so don't worry if yours cracks. As long as it doesn't go thru your pattern you're ok!)
84825
Next, you're going to have to carve a sprue into the material so you can pour your molten metal, and a couple vent lines going out so that air can escape. I only had to carve into one side to do this.
8482784826
Wrap it tightly with wire. If you don't the molten metal will leak out wherever the path of least resistance is.
Next hold it upright in a sand filled pot, or as I did, hold it in the vice. The only issue with the vice is that it tends to crush the mould, but it will hold together well whatever isn't bound with wire.
I melted some pewter to use with this in a ladle. The important thing to remember is that you just want to heat whatever metal you're pouring to just turn liquid before you pour. The longer it stays molten, the more it will burn the mould out. Cuttlefish is a very good heat insulator and takes quite some time to cool.
84829
Go make a sandwich or something and let this have PLENTY of time to cool down. It won't cool as fast as aluminum or steel moulds do, and will take quite some time to solidify.
Then, unwrap the wire, and carefully seperate the halves. If you look closely, you can see the fractures where the vice cracked the mold, so this is only good for one use.
84830
Success!
Now, if you carefully remove the cast object you can re-use the mold. If you're casting gold, silver, or something that melts hotter, the mold will burn too badly to re-use. It stinks like burnt bone, so don't do this in the kitchen!
8483184832
After trimming off the sprue and vent line flash, you can sand/file and finish profiling. I did this as an exercize to see if it would be easy enough to cast some jewlery at home from scrap silver or gold. Since the pewter was so successful, next time I'll be using silver. The above pic shows 3 rings I have cast that are in different stages of profile and polish.
Hope this helps someone else. I know that I never knew about this technique, and was tickled pink to find out how easy this is!
If you buy a shell, go ahead and get 3 or 4 for just in case you make a mistake or break the mould
84834
On the ring finger is my wedding band, the other is the ring I finished.
I'll post some more pics when the crucibles come in that can melt PMs.
Andy
I'm using this technique with a cuttlefish shell that is available at pet stores. They're used by parakeets to chew on. Next time you're buying some ground walnut shells, pick up a few. They're cheap.
Cut it in half with a hacksaw, then start sanding down the soft side on a piece of 80 grit sandpaper on a flat surface.
84822
Get your object you're trying to duplicate and press it half way into one side of your shell, it's pretty soft, but can break if you put too much pressure, so easy does it. (You can also carve freestyle into it if you wanted to, but I'm not that great of an artist.) Next get some small ball bearings and smoosh them into the mould half way as well. These will be used as reference points when you rejoin the halves.
84824
Next, carefully line up the halves and smoosh them together until you have no air gap between the two. This part is where you're most likely to crack the mould if you're not careful. Take them apart, and voila! (you can see the upper left corner is cracked. It will still be wrapped with wire to keep it together, so don't worry if yours cracks. As long as it doesn't go thru your pattern you're ok!)
84825
Next, you're going to have to carve a sprue into the material so you can pour your molten metal, and a couple vent lines going out so that air can escape. I only had to carve into one side to do this.
8482784826
Wrap it tightly with wire. If you don't the molten metal will leak out wherever the path of least resistance is.
Next hold it upright in a sand filled pot, or as I did, hold it in the vice. The only issue with the vice is that it tends to crush the mould, but it will hold together well whatever isn't bound with wire.
I melted some pewter to use with this in a ladle. The important thing to remember is that you just want to heat whatever metal you're pouring to just turn liquid before you pour. The longer it stays molten, the more it will burn the mould out. Cuttlefish is a very good heat insulator and takes quite some time to cool.
84829
Go make a sandwich or something and let this have PLENTY of time to cool down. It won't cool as fast as aluminum or steel moulds do, and will take quite some time to solidify.
Then, unwrap the wire, and carefully seperate the halves. If you look closely, you can see the fractures where the vice cracked the mold, so this is only good for one use.
84830
Success!
Now, if you carefully remove the cast object you can re-use the mold. If you're casting gold, silver, or something that melts hotter, the mold will burn too badly to re-use. It stinks like burnt bone, so don't do this in the kitchen!
8483184832
After trimming off the sprue and vent line flash, you can sand/file and finish profiling. I did this as an exercize to see if it would be easy enough to cast some jewlery at home from scrap silver or gold. Since the pewter was so successful, next time I'll be using silver. The above pic shows 3 rings I have cast that are in different stages of profile and polish.
Hope this helps someone else. I know that I never knew about this technique, and was tickled pink to find out how easy this is!
If you buy a shell, go ahead and get 3 or 4 for just in case you make a mistake or break the mould
84834
On the ring finger is my wedding band, the other is the ring I finished.
I'll post some more pics when the crucibles come in that can melt PMs.
Andy