Trying to make a Latex Mold from Metal TARDIS

[Vandark]

Hi there,

I'm trying to make a Latex Mold from a Metal TARDIS miniature that I had made.

I'm applying the latex by brush to the surface in layers and blowing with a hairdryer between each.

My problem is, once the mold gets to a certain thickness, I think the weight is pulling the latex from the metal surface and creating air pockets, making the mold bow out slightly.

Has anybody got any tips that could help me, without destroying or damaging the Metal original?

thanks for any help you can give.

Richard

 

[stormtrooperguy]

Any reason not to use a pour on silicone instead? Put a box around it, pour the silicone from the top, let it dry, then pop the tardis out? I bet it could come out without any seams if you use a silicone with a good tear strength / elasticity and don't make the walls too thick.

 

[Vandark]

Any reason not to use a pour on silicone instead? Put a box around it, pour the silicone from the top, let it dry, then pop the tardis out? I bet it could come out without any seams if you use a silicone with a good tear strength / elasticity and don't make the walls too thick.

If I were to use silicone, would I be able to cast plaster into it?

I've been thinking of getting some Smooth-On Rebound 25 rubber for another project, would that be suitable for this project too.

I've never used silicone rubber before, i'm kind of afraid of it.

thanks

RV

 

[jedimaster]

Definately use silicon, it kind of replaced latex for molding about 20 years ago and picks up much more detail. As stormtrooperguy said you could build the box over the tardis and pour in the silicon or use brush on silicon. If your worried about tearing when you pull out the tardis you could add bandage strips between layers of silicon. That's what I did with my clone helmet mold. I can peel the mold off the helmet like a mask which turns it inside out without tearing. But definately go silicon.

 

[Vandark]

Sounds like Silicone is the answer.

I was wondering, can a brushable rubber be poured too?

Also, what's the advantage of brushable over pourable?

thanks

RV

 

[Etewaf]

If you are referring to a brushable latex rubber, no, I don't believe it can be poured. You can mix a small batch of the silicon and brush on a thin layer if you are concerned about air pockets and whatnot, and then pour the rest of the mold.

Brushable is nice when you are doing a jacket mold around an inch or less thick that will have a plaster or fiberglass mothermold over it. But for small models and props, such as the TARDIS you are talking about, a pourable silicon will do the trick.

 

[Beaker]

Rebound shouldn't be poured, the viscosity is to high... if you are new to silicone, try Mold Star 15 (Mold Star® Silicone | Silicone Rubber, Urethane Rubber, Liquid Plastic, Casting Resin, Lifecasting, Epoxy Resin, Rigid and Flexible Foam from Smooth-On) as the pouring silicone to use.. great 'starter' silicone, it is a 1:1 by volume mix that does not need to be vacuumed or pressured... simply mix and pour... being a platinum it has good tear strength and a potential library life of 30+ years... and a WHOLE lot less shrinkage than you will ever get from latex...

 

[Nwerke]

I back going with silicone, it is not cheap but is never the wrong move. And yes, you can cast with plaster, but resin would be better.

How big is your model, though? If it's a small metal casting then just build a box around it with lego, moulding clay, whatever. Make sure it's stuck down well then drown it in silicone. Mix the catalyst in very well, and brush the TARDIS with mixed silicone to be sure you don't have trapped air bubbles.

If it is quite large, it may be a lot cheaper to use brushable silicone. You can make silicone brushable by using a thixotropic additive. Talk to the supplier about what is suitable. You will want to build up two or three layers or more, and once set you should back the mould with plaster or fibreglass to make it rigid, because it will be thinner and floppier than a poured mould. The jacket may have to be made in two parts for ease of use.

With latex, you can have success if you laminate tissue into the mould - not in your first layer obviously, but after that. It will add enough rigidity to prevent some of the peeling and shrinking problems you're having. However you will never get a perfectly flat unwarped surface with latex.

 

[Vandark]

The TARDIS is about 8inches high, so I think ill get some of that MoldStar rubber and have a go at pouring into Lego mold box.

I imagine that MoldStar is the pourable equialent of Rebound?

Thanks for all your help, some good advice there.

I'll post some photos when I get it finished.

 

[Muzza]

The good thing when using silicone as a mold material will last a lot longer than many other moulding materials plus when you are finished with it, or the mold is used up and can't produce anymore you are able to cut it up and reuse the piece in to another mold. Use like a filler to bulk out areas.

Just remember to wear safty glasses whem mixing the catalist to the silicone as the catilist is like water and the you are going to try mixing it in to a thick material you dont want it to splash, and wear gloves as well.
Dont forget to weigh and measure the parts correctly as it is a pain to see your mold not setting.

 

[Azurial]

in response to the original post - i've seen heat cause air bubbles form in curing latex. my advice would be to keep the mold room temp until it cures, and besure to use a decent release agent

 

[TK648]

If I were to use silicone, would I be able to cast plaster into it?

I've been thinking of getting some Smooth-On Rebound 25 rubber for another project, would that be suitable for this project too.

I've never used silicone rubber before, i'm kind of afraid of it.

thanks

RV

You just answered your question, I have been thinking of using a smooth-on
product, Then just call them for your answer go to
Mold Making and Casting Materials Silicone Rubber, Urethane Rubber, Liquid Plastic, Casting Resin, Lifecasting, Epoxy Resin, Rigid and Flexible Foam from Smooth-On for their number or look up their free mold making videos at their sight or on You Tube.

Smooth-On All the way.........................

 

[trekpropguy]

If I were to use silicone, would I be able to cast plaster into it?

I've been thinking of getting some Smooth-On Rebound 25 rubber for another project, would that be suitable for this project too.

I've never used silicone rubber before, i'm kind of afraid of it.

thanks

RV

Get Smooth on OOMOO 30.
It's a lot better for what you want.
And pour it into a box, don't paint it on.

 

[piehead]

just one thing, if the mold star is a platinum silicone and you have used latex on your tardis you may get curing issues. platinums do not like latex or sulphur at all. if you can thouroughly clean the tardis you may be fine. otherwise i would go with a tin cure silicone.

 

[SUPERprops]

Sounds like Silicone is the answer.

I was wondering, can a brushable rubber be poured too?

Also, what's the advantage of brushable over pourable?

thanks

RV

Rebound shouldn't be poured, the viscosity is to high... edit...

Actually Rebound 25 can be poured, I've read it on Smooth-ons' web site and have done it myself(recently). You would think it would be too thick, but it's not until about 10 to 15 minutes after you mix it.

 

[Vandark]

I'm from the UK, does andbody know the best place to get Smooth-On advice from and prices from?

I've tried e-mailing a place called Bentley Chemicals over the years but I never get a reply.

Smooth-On themselves never answer my e-mail questions either.