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Melody wrote:SPark wrote:Quote:
I’d been visualizing a flexible rubber mold for a shape inside, just like the molds on the outside. Maybe one that you poured water into to give it support and shape, and then when it’s hardened you dump the water out and pull the mold off from the inside.
That was the theory behind the wax filled one. Water wouldn’t work because it is lighter than the liquid gypsum, and would just be pushed up out of the inner mold. Wax would be rigid, then get melted somehow, and poured out after the piece sets.
What else could fill an inner mold and be poured out… Ball bearings? Sand? those are too heavy…hmmmI have some body parts you could put in there. haha.
J/K
Just a thought….
What about attaching some sort of armature to the outside of the mold that would hold a core form of heavier material up and in the propper place while the gypsum sets and then you could pour out or peel out the core mold?
A vaguely remember doing something like this in Art class years ago…..
Just a thought
*** Oh, if you have time (we all know you’re busy)and its not a trade secret, would it be possible to post a description of the casting process? Maybe it would help get the ideas flowing for us.
Can you fill it up, let the outside dry, then drain some in the middle? Thats how my friends did their ceramics. Maybe that is just dumb… 😕
foxfeather wrote:Just a thought….
What about attaching some sort of armature to the outside of the mold that would hold a core form of heavier material up and in the propper place while the gypsum sets and then you could pour out or peel out the core mold?
A vaguely remember doing something like this in Art class years ago…..
Just a thought
*** Oh, if you have time (we all know you’re busy)and its not a trade secret, would it be possible to post a description of the casting process? Maybe it would help get the ideas flowing for us. The pieces are cast upside down. The gypsum is poured into the mold from the bottom of the piece. The molds are very thin glove molds made of silicone rubber that are supported by precisely fitted, two part “carriers” made of gypsum. If you haven’t seen it, there is a picture of an assembled mold and carrier here: http://www.windstoneeditions.com/galleries/displayimage.php?album=16&pos=14
As you can see, often there is very little room to pour the gypsum into the mold. The Secret Keeper, of course, has a much larger bottom area so there is some room to work with, but obstructing the pouring area is a concern too, because the gypsum must have time to run into the mold before it starts to set. Gypsum also gets really HOT when it sets! The larger the piece, the hotter it gets. That is why we thought wax would work well, it would melt when the piece sets. Gypsum also expands a little when it sets, so the core hole would get slightly bigger than whatever you used to mold it with.This is good if you want to remove something,but perhaps it is bad if you want to leave something in place, though I can’t see why voids between the sculpture and the permanent core inside the piece would make a difference. Nobody is going to rattle these things!Except ups.
There is a nice flat surface across the pouring end of the carriers to mount a framework for supporting a form inside the hollow mold.
We do that with cores for several of the pieces, mostly the stone finish things and the rock dragons. They are silicone plugs that pull straight out of the sculpture. We could make a small, straight core in the bottom of the Secret Keeper, but it wouldn’t gain us too much.skigod377 wrote:Can you fill it up, let the outside dry, then drain some in the middle? Thats how my friends did their ceramics. Maybe that is just dumb… 😕
Gyspum sets up all at once, so there isn’t a time when the outside is set, and the inside isn’t, though we did try rotational molding. That is done with a machine that rotates the mold while the plaster is setting so that it coats the inside of the mold leaving a hollow inside. It didn’t work for this sculpture, though I know it works, because you see those hollow plaster piggybanks and bulls in all the markets around here. They even got legs.
In case the gallery link is buggared up for anyone else, here are the images directly:
This is what the molds look like that the production pieces are cast into. The plaster carriers form a shell that supports the rubber mold while they are filled.The belt is holding the two-part carriers together around the single piece rubber mold inside. (This is a flion mold)
This is a mold being made on the griffin chick sculpture. The “master” sculpture is still inside of the blue silicone glove mold on the left. The “case” that forms the outside shape of the mold is lying behind the painted griffin chick. The case comes apart into two halves . You can see the thin flashing that is still on the blue rubber mold where the silicone has creeped up between the two halves of the case. Silicone flows into even the tiniest crevice, that is why it so good for reproducing fine detail
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My art: featherdust.comBecause they take a long time to dry and they don’t have enough space to store them. They are also cost a lot to ship and if the SK has a defect then they (stores/customers) would have to ship them back to the factory.
How about glass bubbles/beads instead of sand? Ultra light, but compacts like sand and can be drained out like sand. I don’t think they are affected by heat. Heck, we mix them in our potting material to make it lighter. Not sure what that would do to gypsum, but I bet it would be cool to find out!
I could probably come up with a sample if you wanted to try it.I just realized you probably don’t know the consistancy of the beads I’m talking about. They are tiny. They look like a fine powder, but they are little glass beads. I think people also use it for sand blasting too.
We use it to mix in our potting material as we have strict weight measurements we have to meet. We also put it through extreme ESS. I don’t know how hot the gypsum gets when it cures, but I don’t think it would affect the beads.
Anyway, it would be interesting to see what would happen when mixed with your gypsum.
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