1 Piece Latex Mould of a Clay Helmet Disaster

OK, so I was doing a latex mould of a clay helmet, and planned to reinforce it with plaster of paris bandage in a mother mould sort of fashion.

Only my mould completely failed

As the Latex couldn't come off the clay sculpt without first removing the plaster of paris, I attempted to reattach said items, only to have my mould pretty much unworkable and out of shape.

So back to the drawing board - Thuston James' book offers advice on two part mould/casting, rejoining the fibreglass pieces (only I'm not too confident I can do that). I'm still tempted to have another bash at a one piece mould, only I think it'll probably go wrong.

So what I'm asking, is basically what would you do in my situation?

Thanks again

Originally Posted by IonosFear

OK, so I was doing a latex mould of a clay helmet, and planned to reinforce it with plaster of paris bandage in a mother mould sort of fashion.

Only my mould completely failed

As the Latex couldn't come off the clay sculpt without first removing the plaster of paris, I attempted to reattach said items, only to have my mould pretty much unworkable and out of shape.

So back to the drawing board - Thuston James' book offers advice on two part mould/casting, rejoining the fibreglass pieces (only I'm not too confident I can do that). I'm still tempted to have another bash at a one piece mould, only I think it'll probably go wrong.

So what I'm asking, is basically what would you do in my situation?

Thanks again

First I would need to know what type of clay you are using ? wax based, oil ect... after knowing what type of clay you are using, I would suggest what type of molding rubber to use. Also, very important, is your clay sulpher free ?
Clay with sulpher in it cannot be used with any silicone rubbers because the rubber will not dry completely .
So, what type of clay are we speking of ?
You will need to step up to a better rubber, latex has it uses but not for thick molds, there is better stuff thats not to expensive.

http://smoothon.com/rebound.htm

This is the method I'd suggest and the products I'd suggest. This is what we used to get the beehive helmet mold and it came out awesome.

Originally Posted by IonosFear

OK, so I was doing a latex mould of a clay helmet, and planned to reinforce it with plaster of paris bandage in a mother mould sort of fashion.

Only my mould completely failed

As the Latex couldn't come off the clay sculpt without first removing the plaster of paris, I attempted to reattach said items, only to have my mould pretty much unworkable and out of shape.

So back to the drawing board - Thuston James' book offers advice on two part mould/casting, rejoining the fibreglass pieces (only I'm not too confident I can do that). I'm still tempted to have another bash at a one piece mould, only I think it'll probably go wrong.

So what I'm asking, is basically what would you do in my situation?

Thanks again

did you use a mold-release agent?

The problem isn't with the materials at all, as I've used the same method to get some chest and shoulder armour off my sculpts to great effect.

The problem comes that with a rigid one piece mould wrapped around a helmet, I can't remove it without breaking the rigidness of the mother mould, which is near impossible to reattach to form up the shape it moulded, hence the latex flops about and the shape is lost. I've though about attempting a two piece mould, or to have another method of doing a one piece mould - some trick of the trade someone's used to great effect.

Sorry to confuse anyone over that

Sounds like you need a two piece mold or...
The rubber layer should have "keys" built into the rubber so you can press the rubber keys into the mother mold to hold the rubber inplace when casting so it doesn't flop around like you stated above.
It's hard to decsribe how to make the keys here, maybe someone has a sample pic...

What brand of latex are you using? I use liquid latex to make masks and once it cures it shrinks up to 20%

I have noticed some slight shrinkage yeah. Is there a way you can eliminate this so the mother mould sizes up once the latex isn't on the model any more?

Sounds like your experiencing the same problems I had when I made my first stormtrooper face mould.I made a one peice mother mould in plaster and it locked down bad.I had to break it off and fix my sculpt

I ended up making a 3-part mother mould to hold my rubber mould.It's quite easy to make really.Just figure out where you need to make the joints (easier said than done ) and make a clay barrier/wall and then begin with your plaster jacket.Make sure you grease up the edges of the plaster once it's cured or the next part of your mould will stick,and your back to having a one-piece mould

Take your time and you'll work it out

-Paul.

the way to stop it is to not use it, I don't know why they sell it as "mold builder" the shrinkage is from all the water in the mix drying out. Pick up some mold making silicone. doesn't shrink and is more easily flexed than latex.