PDA

View Full Version : Here's a weird casting question...



kpolley
12-18-2006, 11:12 PM
Okay, I am looking to all of you out there who have more experience with casting and mold making than I do on this one. I may be chasing a pipe dream, but I am looking to someone for inspiration.

I have come into possesion of a really cool sculpt, but the piece is about double the size that I would like it to be. I want to end up with a positive of the piece that is about half the size that it is now. Is there some way that I can make a mold off of the piece I have and somehow end up with a smaller version of it. Is there a molding agent that would shrink that much? Has anyone out there ever tried to address a problem like this? I am racking my brain, but I don't know what to do. Any advice, thoughts, or solutions would be greatly appreciated. I am open to anything at this point. Lead me in a direction...PLEASE!

SSP
12-18-2006, 11:21 PM
Just today I went to my friend Kims house for her birthday, she is an amazing artist, showed me her drawings and sculptures, she showed me a couple that were copies of each other but different sizes, both a drawing and a scuplture, I asked her "woa,, how did you get them to copy like that?"

"I redrew them"

Appearently there's no real way (that I or she knows of) that would shrink a sculpture, it would take the artists to re-produce it on a smaller scale. Maybe there is some kind of a shrinking agent, but you'd lose a lot of characteristics. I mean, it probably wouldn't shrink evenly.

That's my best guess, maybe I'm wrong, but I'm just trying to return the favor for your help with Wuffy, thanks again.

PumpkinHead
12-18-2006, 11:27 PM
The only thing I can think of would be to get ahold of a 3-d scanner and a hot-wax digital outputter. The same thing that most toy companies use for scanning celebrities to make action figures.
But ... if you don't have fistfulls of cash to throw at your problem ( upwards of 5 thousand) then I would suggest having an artist do it.

BTW: what is the sculpt and how big is it?

-PH

Greg Chrise
12-19-2006, 12:02 AM
Way back in the late 1700's this guy Thomas Jefferson came up with a machine that would help mint coins. The coin is made 8 inches in diameter, and thick to scale and then it makes a small die cast to make the coins. It involves an arm mechanism that uses a leverage type conversion of the motion over the larger piece to make the smaller one or vica versa.

I can't remember where I have seen them for sale. Perhaps drafting supply catalogs? For $40 to $80 but if you looked up inventions by Tommy there is probably a picture and you could make one. You would have a smaller hunk of clay and run the reference over the larger one to know what to remove and what needs built up. A more sophisticated machine would have a demel tool on it and carve the new one out of plaster or wax or wood.

Artists are trained to put a grid up called a bridge. It looks like an engine pulling gantry only has measurements up the legs and across the top of the new scale that will be transfered or referenced on to the new piece. Of course if it is a drawing there are clear plastic grids and these help put out points on a square block of material as well as a piece of paper. Usually it is the other way around, you do small ones to see what it would look like and then make a bigger one as a full sized sculpture.

These days there are ways to cheat like taking a picture and using a Xerox machine to decide what size the new piece will be and then worry about the reference grid of actual measurments.

dale911
12-19-2006, 06:21 AM
If you want to make a latex copy, make a stone mold of the sculpt. (if it has undercuts, you'll have to make a silicone mold, then make a silicone cast first) Once you have a stone mold (Ultracal 30, Hydrocal, or in this case pottery plaster will work since you're only going to use it once) fill it with latex. Let the latex sit for about 45 minutes to an hour so it thickens well. Then pour the latex out and let it dry for a day or 2. pull it out of the mold and let it sit for a few days to cure. After it has cured, make a mold of it and continue this process until it is small enough. Each generation should shrink 10-20% depending on mold thickness, casting thickness and ambient moisture. Good luck.

Dan Faupel
12-19-2006, 08:58 AM
Kip...one of the only ways to get an accurate reduction in size is to make an alginate mold of your sculpt, let it dry longer than you normally would after demolding and the alginate will shrink up to 30% it's original size without losing much detail....good luck!

SpFXChic
12-19-2006, 09:04 AM
I have to agree with a few of the other posters above. Either resculpt a smaller version of it, or let your alginate dry a bit longer. Either way, it may lose some of the detail in the process.

Raycliff Manor
12-19-2006, 09:41 AM
Hey SpFXChic, in case I haven't mentioned it before... great website!

Kel

kpolley
12-19-2006, 09:49 AM
Thanks to everyone for the help and advice. I think I'll try the alginate idea since I have a bunch of it laying around anyway. I'll let you all know how it went as soon as I have something to tell. Wish me luck.

Infoamtek
12-19-2006, 10:38 AM
This is the stuff you really need:
http://www.sculpt.com/catalog_98/CastingMaterials/HydroShrink.htm

SpFXChic
12-19-2006, 12:04 PM
This is the stuff you really need:
http://www.sculpt.com/catalog_98/CastingMaterials/HydroShrink.htm

Infoamtek to the rescue!!! :)


Kel, thanks for the compliment!

Dan Faupel
12-19-2006, 01:05 PM
Cool stuff Infoamtek!...Kip, try this stuff...looks like maybe more reduction than alginate for what you are working on...

kpolley
12-19-2006, 01:15 PM
Infoamtek, you are a life saver. This is EXACTLy what I wanted. I just never new anything like this actually existed. This is exactly what I am going to do. I am curious, though, about one thing. If you have experience with this stuff maybe you can tell me. Can I pour this material into an alginate mold or do I have to use a rubber mold? Alginate would be great because I have some laying around but I'll spring for the rubber if I have to.

Thanks again. I can't tell you how much this is going to help me.

Jim Warfield
12-19-2006, 09:23 PM
All this marvelous advice on how to shrink a mask or bust. I was going to suggest you simply build a great big room to put the item in and then it would look smaller in such a setting...and that's why I suffer so, wearing this extremely tight underware. ERRGH!