Question about bio mold making

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tommynator1024

Guest
Hi folks, I have several questions about making a mold for a bio. My references are Gene's .rtf file tutorial and a website once posted here from a guy who's giving step by step instructions on how he made a mold for his Ghostbusters Slimer figure. Please assume I've read them but need further input. No need posting a link to those two.

So:

1. The starting point is to sculpt it with clay, right. But when you do, do you sculpt it as a perfect bio (thin like the real deal, no supporting points) or as a bust (a pile of clay with a bio "surface" on top of it)??

I was afraid that a bio done in clay would be too thin to keep it's shape and break apart before I could burn it in the oven. But if I sculpt it as a bust, I would need to do a clay "negative" of the bust for the inside of the bio.

1a. How much liquid silicone would I need?


2. If I use Gene's tutorial and apply the typical bathroom tile sealant silicone with my hands, how do I get a mold from that? I will certainly get a "negative" in silicone, but only one half of it, and I'd still need a supporting frame to keep those two together and in the right shape.
 
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pirkleations

Guest
TM,

If I read your question right, you want to cast both the inside and the outside surface of your bio?

I haven't seen a bio yet that had a "finished" inside surface.

You'll likely only have to do the bio bust sculpt of the front side surface. How smooth and clean the inside of the bio looks once you cast is up to you. But it would make life a bit easier if you just go for the outside surface sculpt. The inside will rarely be seen by human eyes.

When I do(or re-do) my first bio sculpt, I am just sculpting the outer surface. It will keep things easy for me.

And I need things to be as easy as possible!!!

Good luck on your project!!!


DangerDavey
 
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tommynator1024

Guest
That's what I'm always saying, Dave, keep it simple. Or, as our Professor used to say with a heavy french accent, "informaticians are lazy".

I don't really want the inside to be sculpted. It's just that I think you need a second half of the mold. The one half is the imprint of the bio's outside surface, which defines the looks. The other half of the mold prevents the resin from flowing out and defines the thickness of the future cast.

Without that counterpart, you would just put the imprint of the clay bio on the ground and pour resin into it until the thing's running over. But then the thickest spot on the cast would be almost a foot thick.



I'm sorry, I can't describe it any better, and I've never casted before, so I don't have any experience with the stuff.
 
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newburns

Guest
The easiest way to get a thin bio cast would be to brush in a number of small batches of urethane resin rather than just dumping one huge batch into your mold. Let each of the previous layers gel (but don't walk away for 2 hours). You might also want to add afiller such as microballoons to your extra layers to make a thicker material that can be pasted/painted on and built up much easier...

You're thinking in terms of a 2 part mold, a negative, and a core to that negative. While this is a very functional option, it is a LOT more work, and really overkill for a personal piece... If you need to know the process, I'd be happy to explain it in detail, but I would persoanlly recommend sticking to the simple brush-up of layers...

Of course the other option (which is most durable) would be to use fiberglass. A standard size bio could be made VERY durable with only about $20-25 of polyester resin and fiberglass mat/cloth... You'd have one that would be VERY difficult to ever break...

As for molding with caulking, it is a cheap alternative to RTV, but also a very time consuming one. A one piece RTV mold of a bio sized sculpt could be brushed up using accelerator and completely finished and ready to run in as little as 2-3 hours (depending on your working speed and experience of course). It will cost a bit more (about 2 - 2 1/2 times as much $), but you won't need to spread your molding process out for days to even a week or more...

Good luck to you and just remember it's for fun...
Steve
 
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Maverick118

Guest
Well if you add some acrylic paint to the caulking it rapidly accelerates the cure time of it. but I would put a jacket mold on it too as the the caluk type mold is prone to tearing. But in a pinch it is a good alternative to the real deal, but make sure it is 100% silicone.
 
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tommynator1024

Guest
thanks to the both of you, that has been immensely helpful!

Steve, I was under the impression that the resin was too liquid to apply it in layers like you described it. So that's cool. I assume there won't be any problems with the various layers not melting together because they're in different stages of curing?

I was thinking that making a full two-part mold would be overkill, too. I just couldn't see how the other method could work out, so again, thanks!
 
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newburns

Guest
The resin would be too liquidy to apply overall. Apply the first layer or two with a brush just painting it on as is. After those have gelled, you can add several more layers using the filler (microballoons, cabosil, aerosil, etc)... With a filler, you can make the resin more "paste-like" and build more quickly. If you use just straight resin, it will take forever.

Most places that sell urethane resins also carry the fillers. Just inquire...

As for the layers, as long as the previous layer isn't completely set, you will get a chemical bond. If a layer does set, you'll need to lightly sand and scuff it to get the bite from the future layers and the mechanical bond. I would just recommend getting it all done in one session and avoiding the sanding all together...

Good Luck
Steve
 
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darkenism

Guest
ok ive seen the bondo fiberglass resin and the bondo jelly resin at walmart....anyone know if i could i start with the regular resin to catch the details...then move to the jelly since its thicker it would fill it up faster...would the two bond together ???? what do ya think?
 
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acerhater

Guest
How about slush casting it? Make your negitive mold then pour in the resing and start rotating the mold, spreading the resing around the inside in a thin layer. Keep rotating untill the resin sets.
 
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