Splitting a silicone mold into four parts?

[Jeebee25]

Hey guys! I want to make a stunt Ghost trap from Ghostbusters with all the greebles included. I have an idea in my head but have been scouring the web and these forums for information and have come up with zilch. Which makes me think I am missing something important.

Here is my idea -

I want to make a buck of the trap that is complete (except the handle.) Then cover in clay and add my keys. Make a two piece fiberglass jacket that will be then bolted together. After removing my clay, pouring my silicone and etc. etc. I'm sure you know all of this.

But then here is what I want to do but can not find information on. I want to cut the mold into quarters so that it will be easier to de-mold with all the knobs / greebles. My hope is that I can produce a complete trap in fiberglass and that the mold will have a longer life. Has anyone tried this? Is there an issue that my ABSOLUTE AND TOTAL lack of experience is preventing me from seeing? :facepalm

Any help is appreciated.

One more added note: I want to make this as an open bottom mold and then make a separate mold for the bottom and then people can glue the two together.

 

[Jeebee25]

Perhaps I have phrased this wrong? :unsure

 

[DexJay]

Hi, if I understand you correctly if you're going to make a mould in 4 pieces build it that way from the beginning rather than cutting it later.

I think I'd turn the trap buck on its side, then build a window to lay it in so you're just going to mould the right side (for example). Fill the gaps with plasticine and if you're going to mould in quarters build a shutter in the middle with cardboard say and more plasticine.

Pour the silicone and add keys for the front, remove the shutter (add some silicone release spray) then do the back. Make your fibreglass mother mould over the top (in 1 or two pieces) then turn it over to do the other half and repeat. The mother mould could be bolted together in quarters.

Make sense? I made a 2 piece silicone mould and 4 piece mother mould like this for my y-wing helmet.

Hope this makes some sense!
Rich

 

[DexJay]

Kinda like this? See the lower images.. but with a temporary cardboard bit of shuttering in the middle..

http://www.therpf.com/f9/dexs-y-wing-helmet-scratch-build-140510/

 

[Ozymandius]

What you're talking about is commonly called a 'jewelers cut'. It creates a distinctive sawtooth pattern that allows the silicone to key back with itself and align. Just Google "Mold jewelers cut" and you should find plenty of tutorials on it.

That said, I wouldn't think you would need it with a ghost trap as there's just not that much to give you problems. In fact if you're going to do an open faced mold, it would be far more useful to do a one piece silicone mold that's stretchy enough to pull around the knobs and such. This is what I do with my helmet molds and it's a massive time saver.

 

[madmanmoe64]

I'd agree that it's just easier to go with a nice stretchy silicone in a dump mould. But if you want to split it up then start by looking at a 2-part mould.
Basically you set it up so each part of the mould is poured separately. This method can be extended to make as many parts as needed (I've only ever needed 3, working with dense silicone)

I'm not overly familiar with the greebles on the trap so can't give more specific help.

 

[bookface]

If I were going to do a mould in two parts, I would always just start it as a two piece mould, rather than cutting it afterwards, unless it was just a partial cut (up the back of a bust, for example).

My personal preference is for brush on moulds, where you would run a clay shim down the middle of the piece to be moulded (assuming a 2 part mould), brush the silicone onto one side until it's thick enough, then do the mother mould, then remove the clay, and do the other side, remembering to use mould release so the two halves don't stick to each other.

Like madmanmoe, I'm not super familiar with the details of the trap, so I don't even know that doing it in two parts is necessary, but that's how I'd do it if it was.