Plaster casting?

[colu41]

So I've been doing a bit of sand casting. I actually have a few orders from people to try some things out. But I was wondering, casting with some type of plaster, seems to work flawlessy. It just takes more time. 

I have a friend that wants an eagle with it's wings spread out. As I believe I could get close with a sand casting, I also believe a 2 piece "plaster style" mold would be even better. I've seen it done with hollow figures and whatnot but. I don't have a clue what type of plaster it is and how it's mixed. Does anyone have any info? I'd love to try it out. And also wouldn't you think you could use these molds more than once?

Thanks!

[Argentknight]

I have tried casting silver with plaster. The molten silver came into close proximity with some small air bubbles in the plaster. The silver literally exploded out of the mould, as the air expanded rapidly, showering me and the rest of the workshop with molten metal. I learned my lesson - never again.

[colu41]

Man. That sounds messy. So I'm guessing you would have to make air release holes in the mold?

[Argentknight]

The air gets incorporated when mixing the plaster, so you don't know where the air bubbles are. So providing air release holes wouldn't work. When I tried it, the mould was obliterated.

[colu41]

Hm. Possibly using a pressure pot could get the air bubbles out. I might have to give it a try but, it doesn't sound too promising. Thanks!

[999Ag]

Just be careful, the last thing we need is a valued member wounded in action! 

[CurioBullion]

On 05/12/2018 at 06:28, colu41 said:

So I've been doing a bit of sand casting. I actually have a few orders from people to try some things out. But I was wondering, casting with some type of plaster, seems to work flawlessy. It just takes more time. 

I have a friend that wants an eagle with it's wings spread out. As I believe I could get close with a sand casting, I also believe a 2 piece "plaster style" mold would be even better. I've seen it done with hollow figures and whatnot but. I don't have a clue what type of plaster it is and how it's mixed. Does anyone have any info? I'd love to try it out. And also wouldn't you think you could use these molds more than once?

Thanks!

Did you ever end up trying plaster casting? I came to this old post after finding this link for a table top system, with vacuum chamber for degassing the plaster. its a lost wax system but its being done so should work for your two part mold as well. nice video he does say its not plaster of paris, its casting plaster.